Electropaedia Battery History, Technology, Applications and Development

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We think of a battery today as a source of portable power, but it is no exaggeration to say that the battery is one of the most important inventions in the history of mankind. Volta's pile was at first a technical curiosity but this new electrochemical phenomenon very quickly opened the door to new branches of both physics and chemistry and a myriad of discoveries, inventions and applications. The electronics, computers and communications industries, power engineering and much of the chemical industry of today were founded on discoveries made possible by the battery.

It is often overlooked that throughout the nineteenth century, most of the electrical experimenters, inventors and engineers who made these advances possible had to make their own batteries before they could start their investigations. They did not have the benefit of cheap, off the shelf, mass produced batteries. For many years the telegraph, and later the telephone, industries were the only consumers of batteries in modest volumes and it wasn't until the twentieth century that new applications created the demand that made the battery a commodity item.

In recent years batteries have changed out of all recognition. No longer are they simple electrochemical cells. Today the cells are components in battery systems, incorporating electronics and software, power management and control systems, monitoring and protection circuits, communications interfaces and thermal management.

2500 B.C. Sometimes known as the "Second oldest profession", soldering has been known since the Bronze Age (3500 to 1100 B.C.). A form of soldering to join sheets of gold was known to be used by the Chaldeans in Ur and also Mesopotamians (both in modern day Iraq). Fine metal working techniques were also developed in Egypt where filigree jewellery and cloisonné work found in Tutankhamun's tomb dating from 1327 B.C. was made from delicate wires which had been drawn through dies and then soldered in place.

Egypt was also home to Imhotep the first man of science in recorded history. He was the world's first named architect and administrator who around 2725 B.C. built the first pyramid ever constructed, the Stepped Pyramid of Saqqara. Papyri were unearthed in the nineteenth century dating from around 1600 B.C. and 1534 B.C. both of which refer to earlier works attributed to Imhotep. The first outlines surgical treatments for various wounds and diseases and the second contains 877 prescriptions and recipes for treating a variety of medical conditions making Imhotep the world's first recorded physician. Other contemporary papyri described Egyptian mathematics. Egyptian teachings provided the foundation of Greek science and although Imhotep's teachings were known to the Greeks, 2200 years after his death, they assigned the honour of Father of Medicine to Hippocrates.

2300 B.C. The earliest evidence of the art of stenciling used by the Egyptians. Designs were cut into a sheet of papyrus and pigments were applied through the apertures with a brush. The technique was reputed to have been in use in China around the same time but no artifacts remain.

1300 B.C. Fine wire also made by the Egyptians by beating gold sheet and cutting it into strips. Recorded in the Bible, Book of Exodus, Chapter 39, Verse 3, - "And they did beat the gold into thin plates, and cut it into wires, to work it. in the fine linen, with cunning work."

The Egyptians also made coarse glass fibres as early as 1600 B.C. and fibers survive as decorations on Egyptian pottery dating back to 1375 B.C.

1280 B.C. Around this date, after his escape from Egypt, Moses ordered the construction of the Ark of the Covenant to house the tablets of stone on which were writen the original "Ten Commandments". Its construction is described in great detail in the book of Exodus and according to the Bible and Jewish legend it was endowed with miraculous powers including emitting sparks and fire and striking dead Aaron's sons and others who touched it. It was basically a wooden box of acacia wood lined with gold and also overlaid on the outside with gold. The lid was decorated with two "cherubim" with outstretched wings. In 1915 Nikola Tesla, in an essay entitled "The Fairy Tale of Electricity" promoting the appreciation of electrical developments, proposed what seemed a plausible explanation for some of the magical powers of the Ark. He claimed that the gold sheaths separated by the dry acacia wood effectively formed a large capacitor on which a static electrical charge could be built up by friction from the curtains around the Ark and this accounted for the sparks and the electrocution of Aaron's sons.

Recent calculations have shown however that the capacitance of the box would be in the order of 200 picofarads and such a capacitor would need to be charged to 100,000 volts to store even 1 joule of electrical energy, not nearly enough to cause electrocution. It seems Tesla's explanation was appropriately named.

800 B.C. The magnetic properties of the naturally occurring lodestone were first mentioned in Greek texts. Also called magnetite, lodestone is a magnetic oxide of iron (Fe₃O₄) which was mined in the province of Magnesia in Thessaly from where the magnet gets its name. Lodestone was also known in China at that time where it was known as "love stone" and is in fact quite common throughout the world.

Surprisingly although they were aware of its magnetic properties, neither the Greeks nor the Romans seem to have discovered its directive property.

Eight hundred years later in 77 A.D., the somewhat unscientific Roman chronicler of science Pliny the Elder, completed his celebrated series of books entitled "Natural History". In it he attributed the name "magnet" to the supposed discoverer of lodestone, the shepherd Magnes, "the nails of whose shoes and the tip of whose staff stuck fast in a magnetic field while he pastured his flocks". Thus another myth was born. Pliny was killed during the volcanic eruption of Mount Vesuvius near Pompeii in A.D. 79 but his "Natural History" lived on as an authority on scientific matters up to the Middle Ages.

600 B.C. The Greek philosopher and scientist, Thales of Miletus - one of the Seven Wise Men of Greece - demonstrated the effect of static electricity by picking up small items with an amber rod made of fossilised resin which had been rubbed with a cloth. He also noted that iron was attracted to lodestone.

Thales was the first thinker to attempt to explain natural phenomena by means of some underlying scientific principle rather than by attributing them to the whim of the Gods - a major departure from previous wisdom and the foundation of scientific method.

Thales left no writings - knowledge of him is derived from an account in Aristotle's Metaphysics.

460 B.C. Another Greek philosopher Democritus of Abdera developed the idea that matter could be broken down into very small indivisible particles which he called atoms. Subsequently Aristotle dismissed Democtritus' atomic theory as worthless and Aristotle's views tended to prevail. It was not until 1803 that Democritus' theory was resurrected by John Dalton.

350 B.C. The Greek philosopher and scientist Aristotle (384-322 B.C.) provided "scientific" theories based on pure "reason" for everything from the structure of the cosmos down to the four fundamental elements earth, fire, air and water.

Aristotle believed that knowledge should be gained by pure thought and had no time for mathematics which he regarded only as a calculating device. Neither did he support the experimental method of scientific discovery which he considered inferior. In his support it should be mentioned that the range of experiments he could possibly undertake was limited by the lack of accurate measuring instruments in his time and it was only in the seventeenth century that instruments such as microscopes, telescopes, clocks with minute hands, accurate weighing equipment, thermometers and manometers started to become available.

Unfortunately Aristotle's "rational" explanations were subsequently taken up by St Thomas Aquinas (1225-1274) and espoused by the church which for many years made it difficult, if not dangerous, to propose alternative theories. Aristotle's theories of the cosmos and chemistry thus held sway for 2000 years hampering scientific progress until they were finally debunked by Newton and Lavoisier who showed that natural phenomena could be described by mathematical laws.

250 B.C. The Baghdad Battery - In 1936 several unusual earthenware jars, dating from about 250 B.C., were unearthed during archeological excavations at Khujut Rabu near Baghdad. A typical jar was 130 mm (5-1/2 inches) high and contained a copper cylinder, the bottom of which was capped by a copper disk and sealed with bitumen or asphalt. An iron rod was suspended from an asphalt stopper at the top of the copper cylinder into the centre of the cylinder. The rod showed evidence of having been corroded with an acidic agent such as wine or vinegar. 250 BC corresponds to the Parthian occupation of Mesopotamia (modern day Iraq) and the the jars were held in Iraq's State Museum in Baghdad. In 1938 they were examined by German archeologist Wilhelm König who concluded that they were Galvanic cells or batteries supposedly used for gilding silver by electroplating. A mysterious anachronism. Backing up his claim, König also found copper vases plated with silver dating from earlier periods in the Baghdad Museum and other evidence of (electro?)plated articles from Egypt. Since then, several replica batteries have been made using various electrolytes including copper sulphate and grape juice generating voltages from half a Volt to over one Volt and they have successfully been used to demonstrate the electroplating of silver with gold. One further, more recent, suggestion by Paul T. Keyser a specialist in Neat Eastern Studies from the University of Alberta is that the galvanic cells were used for analgesia. There is evidence that electric eels had been used to numb an area of pain, but quite how that worked with such a low voltage battery is not explained. Apart from that, no other compelling explanation of the purpose of these artifacts has been proposed and the enigma still remains.

Despite warnings about the safety of these priceless articles before the 2003 invasion of Iraq, they were plundered from the museum during the war and their whereabouts is now unknown.

The Parthians were nomadic a nomadic tribe of skilled warriors and not noted for their scientific achievements. The importance of such an unusual electrical phenomenon seems to have gone completely unrecorded within the Parthian and contemporary cultures and then to have been completely forgotten despite extensive historical records from the period.

There are also some features about the artifacts themselves which do not support the battery theory. The asphalt completely covers the copper cylinder, electrically insulating it so that no current could be drawn without modifying the design and no wires, conductors, or any other sort of electrical equipment associated with the artifacts have been found. Furthermore the asphalt seal forms a perfect seal for preventing leakage of the electrolyte but it would be extremely inconvenient for a primary galvanic cell which would require frequent replacement of the electrolyte. As an alternative explanation for these objects, it has been noted that they resemble storage vessels for sacred scrolls. It would not be at all surprising if any papyrus or parchment inside had completely rotted away, perhaps leaving a trace of slightly acidic organic residue.

220-206 B.C. The magnetic compass was invented by the Chinese during the Qin (Chin) Dynasty, named after China's first emperor Qin Shi Huang di, the man who built the wall. It was used by imperial magicians mostly for geomancy (Feng Shui and fortune telling) but the "Mighty Qin's" military commanders were supposed to be the first to use a lodestone as a compass for navigation. Chinese compasses point south.

27 B.C. - 5th Century A.D. The Roman Empire. The Romans were great plumbers but poor electricians.

The Romans were deservedly renowned for their civil engineering - buildings, roads, bridges, aqueducts, central heating and baths. Surprisingly however, in 500 years, they didn't advance significantly on the legacies of mathematics and scientific theories left to them by the Greeks. Fortunately, the works of the Greek philosophers and mathematicians were preserved by Arab scholars who translated them into Arabic.

200 Greek philosopher Claudius Galen from Pergamum, Asia Minor, physician to five Roman emperors and surgeon to the Roman gladiators, was the first of many to claim therapeutic powers of magnets and to use them in his treatments.

426 Electric and magnetic phenomena were investigated by St Augustine who is said to have been "thunderstruck" on witnessing a magnet lift a chain of rings. In his book "City of God" he uses the example of magnetic phenomena to defend the idea of miracles. Magnetism could not be explained but it manifestly existed, so miracles should not be dismissed just because they could not be explained.

619 In 1999, archaeologists at Nendrum on Mahee Island in Ireland investigating what they thought to be a stone tidal pond used for catching fish uncovered two stone built tidal mills with a millstones and paddle blades dating from 619 AD and 787 AD. Several tidal mills were buillt during the Roman occupation of England for grinding grain and corn. They operated by storing water behind a dam during high tide, and letting it out to power the mill after the tide had receded and were the forerunners of the modern schemes for capturing tidal energy.

645 Xuan Zhuang the great apostle of Chinese Buddhism returned to China from India with Buddhist images and more than 650 Sanskrit Buddhist scriptures which were reproduced in large quantities giving impetus to the refinement of traditional methods of printing using stencils and inked squeezes first used by the Egyptians. A pattern of rows of tiny dots was made in a sheet of paper which was pressed down on top of a blank sheet and ink was forced through the holes. Later stencils developed by the Chinese and Japanese used human hair or silk thread to tie delicate isolated parts into the general pattern but there was no fabric backing to hold the whole image together. The stencil image was printed using a large soft brush, which did not damage the delicate paper pattern or the fine ties. These printing techniques of composite inked squeezes and stencils foreshadowed modern silk screen printing which was not patented until 1907.

700 - 1100 Islamic Science During Roman times, the flame of Greek science was maintained by Arab scholars who translated Greek scientific works into Arabic. From 700 A.D. however, when most of Europe was still in the Dark Ages, scientific developments were carried forward on a broad front by the Muslim world with advances in astronomy, mathematics, physics, chemistry and medicine. Chemistry (Arabic Al Khimiya "pour together", "weld") was indeed the invention of the Muslims who carried out pioneering work over three centuries putting chemistry to practical uses in the refinement of metals, dyeing, glass making and medicine. In those days the notion of alchemy also included what we would today call chemistry. Among the many notable muslim scientists from this period were Jabir Ibn Haiyan, Al-Khawarizmi and Al-Razi.

By the tenth century however, according to historian Toby Huff, the preeminence of Islamic science began to wane. It had flourished in the previous three centuries while Muslims were in the minority in the Islamic regions however, starting in the tenth century, widespread conversion to Islam took place and as the influence of Islam increased, so the tolerance of alternative educational and professional institutions and the radical ideas of freethinkers decreased. They were dealt a further blow in 1485, thirty five years after the invention of the printing press, when the Ottoman Sultan Byazid II issued an order forbidding the printing of Arabic letters by machines. Arabic texts had to be translated into Latin for publication and this no doubt hampered both the spread of Islamic science and ideas as well as the influence of the outside world on the Islamic community. This prohibition of printing was strictly enforced by subsequent Ottoman rulers until 1728 when the first printing press was established in Istanbul but due to objections on religious grounds it closed down in 1742 and the first Koran was not printed in Istanbul until 1875. Meanwhile in 1734 Deacon Abdalla Zakhir of the Greek Catholic Maronite Monastery of Saint John Sabigh in the Lebanon managed to establish the first independent Arabic printing press.

Islam was not alone in banning the dissemination of subversive or inconvenient ideas. Henry VIII in 1529, aware of the power of the press, became the first monarch to publish a list of banned books though he did not go so far as banning printing. He was later joined by others. In 1632 Galileo's book "Dialogue Concerning the Two Chief World Systems", in which he asserted that the earth revolved around the sun rather than the other way round, was placed by Pope Urban VIII on the index of banned books and Galileo was placed under house arrest. Despite these setbacks, European scientific institutions overcame the challenges by the church, taking over the flame carried by the Arabs and the sixteenth and seventeenth centuries became the age of Scientific Revolution in Europe.

776 Persian chemist Abu Musa Jabir Ibn Haiyan (721-815), also known as Geber, was the first to put chemistry on a scientific footing, laying great emphasis on the importance of formal experimentation. In the period around 776 A.D. he perfected the techniques of crystallisation, distillation, calcination, sublimation and evaporation and developed several instruments including the alembic (Arabic al-ambiq, "still") which simplified the process of distillation, for carrying them out. He isolated or prepared several chemical compounds for the first time, notably nitric, hydrochloric, citric and tartaric acids and published a series of books describing his work which were used as classic works on alchemy until the fourteenth century. Unfortunately the books were added to, under Geber's name, by various translators in the intervening period leading to some confusion about the extent of Geber's original work.

830 Around the year 830, Baghdad born mathematician Mohammad Bin Musa Al-Khawarizmi (770-840) published "The Compendium Book on Calculation by Completion and Balancing" in which he introduced the principles of algebra (Arabic Al-jabr "the reduction" i.e. of complicated relationships to a simpler language of symbols) which he developed for solving linear and quadratic equations. He also introduced the decimal system of Hindu-Arabic numerals to Europe as well as the concept of zero, a mathematical device at the time unknown in Europe used to Roman numerals. Al-Khawarizmi also constructed trigonometric tables for calculating the sine functions. The word algorithm (algorizm) is named after him.

920 Around the year 920, Persian chemist Mohammad Ibn Zakariya Al-Razi (865-925), known in the West as Rhazes, carried on Geber's work and prepared sulphuric acid, the "work horse" of modern chemistry and a vital component in the world's most common battery. He also prepared ethanol, which was used for medicinal applications, and described how to prepare alkali (Al-Qali, the salt work ashes, potash) from oak ashes. Al-Razi published his work on alchemy in his "Book of Secrets". The precise amounts of the substances he specified in his recipes demonstrates an understanding of what we would now call stoichiometry.

Several more words for chemicals are derived from their Arabic roots including alcohol (Al Kuhl" "essence", usually referring to ethanol) as well as arsenic and borax.

1040 Thermoremanent magnetisation described in the Wu Ching Tsung Yao "Compendium of Military Technology" in China. Compass needles were made by heating a thin piece of iron, often in the shape of a fish, to a temperature above the Curie Point then cooling it in line with the earth's magnetic field.

1041 Between 1041 and 1048 Chinese craftsman Pi Sheng produced the first printing press to use moveable type. Although his designs achieved widespread use in China, it was another four hundred years before the printing press was "invented" by Johann Gutenberg in Europe.

1086 Chinese astronomer, cartographer and mathematician Shen Kua, in his Dream Pool Essays, describes the compass and its use for navigation and cartography as well as Pi Sheng's printing technique.

1190 The magnetic compass "invented" in Europe 1400 years after the Chinese. Described for the first time in the west by a St Albans monk Alexander Neckam in his treatise De Naturis Rerum.

1250's Italian theologian St Thomas Aquinas stands up for the cause of "reason" reconciling the philosophy of Aristotle with Christian doctrine. Challenging Aristotle now became a challenge to the Church.

1269 Petrus Peregrinus de Marincourt, (Peter the Pilgrim) a French Crusader, used a compass to map the magnetic field of a lodestone. He discovered that a magnet had two magnetic poles, North and South and was the first to describe the phenomena of attraction and repulsion. He also speculated that these forces could be harnessed in a machine.

1368-1644 China's Ming dynasty. When the Ming dynasty came into power, China was the most advanced nation on earth. During the Dark Ages in Europe, China had developed the compass, gunpowder, paper, paper money, canals and locks, block printing, moveable type, porcelain, pasta and many other inventions centuries before they were "invented" by the Europeans. They were so far ahead of Europe that when Marco Polo described these wondrous inventions in 1295 on his return to Venice from China he was branded a liar. China's innovation was based on practical inventions founded on empirical studies, but their inventiveness seems to have deserted them during the Ming dynasty and subsequently during the Qing (Ching) dynasty (1644 - 1911). China never developed a theoretical science base and the industrial revolution passed China by. Why should this be?

It is said that the answer lies in Chinese culture, to some extent Confucianism but particularly Daoism (Taoism) whose teachings promoted harmony with nature whereas Western aspirations were the control of nature. However these conditions existed before the Ming when China's innovation led the world. A more likely explanation can be found in China's imperial political system in which a massive society was rigidly controlled by all-powerful emperors through a relatively small cadre of professional administrators (Mandarins) whose qualifications were narrowly based on their knowledge of Confucian ideals. If the emperor was interested in something, it happened, if he wasn't, it didn't happen.

The turning point in China's technological dominance came when the Ming emperor Xuande came to power in 1426. Admiral Zheng He, a muslim eunuch, castrated as a boy when the Chinese conquered his tribe, had recently completed an audacious voyage of exploration on behalf of a previous Ming emperor Yongle to assert China's control of all of the known world and to extract tributary from its intended subjects. But his new master considered the benefits did not justify the huge expense of Zheng's fleet of 62 enormous nine masted junks and 225 smaller supply ships with their 27,000 crew. The emperor mothballed the fleet and henceforth forbade the construction of any ships with more than two masts, curbing China's aspirations as a maritime power and putting an end to its expansionist goals, a xenophobic policy which has lasted until current times.

The result was that during both the Ming and the Qing dynasties a succession of complacent, conservative emperors cocooned in prodigious, obscene wealth, remote even from their own subjects, lived in complete isolation and ignorance of the rest of the world. Foreign influences, new ideas, and an independent merchant class who sponsored them, threatened their power and were consequently suppressed. By contrast the West was populated by smaller, diverse and independent nations competing with eachother. Merchant classes were encouraged and innovation flourished as each struggled to gain competitive or military advantage.

Times have changed. Currently China is producing two million graduates per year, sixty percent of which are in science and technology subjects, three times as many as in the USA.

After Japan, China is the second largest battery producer in the world and growing fast.

1450 German goldsmith and calligrapher Johann Genstleisch zum Gutenberg from Mainz invented the printing press, considered to be one of the most important inventions in human history. For the first time knowledge and ideas could be recorded and disseminated to a much wider public than had previously been possible using hand written texts and its use spread rapidly throughout Europe. Intellectual life was no longer the exclusive domain of the church and the court and an era of enlightenment was ushered in with science, literature, religious and political texts becoming available to the masses who in turn had the facility to publish their own views challenging the status quo. Nowadays the Internet is bringing about a similar revolution.

Although it was new to Europe, the Chinese had already invented printing with moveable type four hundred years earlier but, because of China's isolation, these developments never reached Europe.

Gutenberg printed Bibles and supported himself by printing indulgences, slips of paper sold by the Catholic Church to secure remission of the temporal punishments in Purgatory for sins committed in this life. He was a poor businessman and made little money from his printing system and depended on subsidies from the Archbishop of Mainz. Because he spent what little money he had on alcohol, the Archbishop arranged for him to be paid in food and lodging, instead of cash. Gutenberg died penniless in 1468.

1474 The first patent law, a statute issued by the Republic of Venice, provided for the grant of exclusive rights for limited periods to the makers of inventions. It was a law designed more to protect the economy of the state than the rights of the inventor since, as the result of its declining naval power, Venice was changing its focus from trading to manufacturing. The Republic required to be informed of all new and inventive devices, once they had been put into practice, so that they could take action against potential infringers.

1499 The first patent for an invention was granted by King Henry VI to Flemish-born John of Utynam for a method of making stained glass, required for the windows of Eton College giving John a 20-year monopoly. The Crown thus started making specific grants of privilege to favoured manufacturers and traders, signified by Letters Patent, open letters marked with the King's Great Seal.

The system was open to corruption and in 1623 the Statute of Monopolies was enacted to curb these abuses. It was a fundamental change to patent law which took away the rights of the Crown to create trading monopolies and guaranteed the inventor the legal right of patents instead of depending on the royal prerogative. So called patent law, or more generally intellectual property law, has undergone many changes since then to encompass new concepts such as copyrights and trademarks and is still evolving as and new technologies such as software and genetics demand new rules.

1515 Leonardo da Vinci proposed the use of a large concave mirror to capture solar energy to heat water in a boiler used in a dye works.

1593 The thermometer invented by Italian astronomer and physicist Galileo Galilei. It has been variously called an air thermometer or a water thermometer but it was called a thermoscope at the time. His "thermometer" consisted of a glass bulb at the end of a long glass tube held vertically with the open end immersed in a vessel of water. As the temperature changed the water would rise or fall in the tube due to the contraction or expansion of the air. It was sensitive to air pressure and could only be used to indicate temperature changes since it had no scale. In 1612 Italian Santorio Santorio added a scale to the apparatus creating the first true thermometer and for the first time, temperatures could be quantified.

There is no evidence that the decorative, so called, Galileo thermometers based on the Archimedes principle were invented by Galileo or that he ever saw one. They are comprised of several sealed glass floats in a sealed liquid filled glass cylinder. The density of the liquid varies with the temperature and the floats are designed with different densities so as to float or sink at different temperatures. There were however thriving glass blowing and thermometer crafts based in Florence (Tuscany) where the Academia del Cimento, which was noted for its instrument making, produced many of these thermometers also known as Florentine thermometers or Infingardi (Lazy-Ones) or Termometros Lentos (Slow) because of the slowness of the motion of the small floating spheres in the alcohol of the vial. It is quite likely that these designs were the work of the Grand Duke of Tuscany Ferdinand II who had a special interest in thermometers and meteorology.

1600 William Gilbert of Colchester, physician to Queen Elizabeth I of England published "De Magnete" (On the Magnet) the first ever work of experimental physics. In it he distinguished for the first time static electric forces from magnetic forces. He discovered that the earth is a giant magnet just like one of the stones of Peregrinus, explaining how compasses work. He is credited with coining the word "electric" which comes from the Greek word "elektron" meaning amber.

Many wondrous powers have been ascribed to magnets and to this day magnetic bracelets are believed by some to have therapeutic benefits. In Gilbert's time it was believed that an adulteress could be identified by placing a magnet under her pillow. This would cause her to scream or be thrown out of bed as she slept.

Gilbert proved amongst other things that the smell of garlic did not affect a ship's compass. It is not known whether he experimented with adulteresses in his bed.

Gilbert was the English champion of the experimental method of scientific discovery considered inferior to rational thought by the Greek philosopher Aristotle and his followers. He held the Copernican view, dangerous at the time, that the world was not the centre of the universe. He was a contemporary of the more famous Italian astronomer Galileo Galilei (1564-1642) who made a principled stand in defence of the founding of physics on scientific method and precise measurements rather than on metaphysical principles and formal logic. These views brought Galileo into serious confrontation with the church and he was tried and punished for his heresies.

Gilbert died of Bubonic plague in 1603 leaving his books, globes, instruments and minerals to the College of Physicians but they were destroyed in 1666 in the great fire of London which mercifully also brought the plague to an end.

1603 Italian shoemaker and part-time alchemist from Bologna, Vincenzo Cascariolo, searching for the "Philosopher's Stone" for turning common metals into Gold discovered phosphorescence instead. He heated a mixture of powdered coal and heavy spar (Barium sulphate) and spread it over an iron bar. It did not turn into Gold when it cooled, as expected, but he was astonished to see it glow in the dark. Though the glow faded it could be "reanimated" by exposing it to the sun and so became known as "lapis solaris" or "sun stone", a primitive method of solar energy storage in chemical form.

1605 A five digit encryption code consisting only of the letters "a" and "b" giving 32 combinations to represent the letters of the alphabet was devised by English philosopher and lawyer Francis Bacon. He called it a biliteral code. It is directly equivalent to the five bit binary Baudot code of ones and zeros used for over 100 years for transmitting data in twentieth century telegraphic communications.

More importantly Bacon, together with Gilbert, was an early champion of scientific method although it is not known whether they ever met.

Bacon died as a result of one of his experiments. He investigated preserving meat by stuffing a chicken with snow. The experiment was a success but Bacon died of bronchitis contracted either from the cold chicken or from the damp bed, reserved for VIP's and unused for a year, where he was sent to recover from his chill.

There are many "Baconians" who claim today that at least some of Shakespeare's plays were actually written by Bacon. One of the many arguments put forward is that only Bacon possessed the necessary wide range of knowledge and erudition displayed in Shakespeare's plays.

1629 Italian Jesuit priest Nicolo Cabeo published Philosophia Magnetica in which electric repulsion is identified for the first time.

1643 Evangelista Torricelli served as Galileo's secretary and succeeded him as court mathematician to Grand Duke Ferdinand II and in 1643 made the world's first barometer for measuring atmospheric pressure by balancing the pressure force, due to the weight of the atmosphere, against the weight of a column of mercury.

1644 French philosopher and mathematician René Descartes published Principia Philosophiae in which he attempts to put the whole universe on a mathematical foundation reducing the study to one of mechanics. Considered to be the first of the modern school of mathematics, he believed that Aristotle's logic was an unsatisfactory means of acquiring knowledge and that only mathematics provided the truth so that all reason must be based on mathematics.

His most important work La Géométrie, published in 1637, includes his application of algebra to geometry from which we now have Cartesian geometry.

Descartes accepted sponsorship by Queen Christina of Sweden who persuaded him to go to Stockholm. Her daily routine started at 5.00 a.m. whereas Descartes was used to rising at at 11 o'clock. After only a few months in the cold northern climate, walking to the palace for 5 o'clock every morning, he died of pneumonia.

1646 The word Electricity coined by English physician Robert Browne even though he contributed nothing else to the science.

1651 German chemist Johann Rudolf Glauber in his "Practise on Philosophical Furnaces" describes a safety valve for use on chemical retorts. It consisted of a conical valve with a lead cap which would lift in response to excessive pressure in the retort allowing vapour to escape and the pressure to fall. The weight of the cap would reseat the valve once the pressure returned to an acceptable level. Today, modern implementations of Glauber's valve are the basis of the pressure vents incorporated into sealed batteries to prevent rupture of the cells due to pressure build up.

In 1658 Glauber published Opera Omnia Chymica "Complete Works of Chemistry", a description of different techniques for use in chemistry which was widely reprinted.

1654 The first sealed liquid-in-glass thermometer produced by the artisan Mariani at the Accademia del Cimento in Florence for the Grand Duke of Tuscany, Ferdinand II. It used alcohol as the expanding liquid but was inaccurate in absolute terms, although his thermometers agreed with eachother, and there was no standardised scale in use.

1661 Dutch physicist and astronomer Christiaan Huygens invents the U tube manometer, a modification of Torricelli's barometer, for determining gas pressure differences. In a typical "U Tube" manometer the difference in pressure (really a difference in force) between the ends of the tube is balanced against the weight of a column of liquid. The gauges are only suitable for measuring low pressures, most gauges recording the difference between the fluid pressure and the local atmospheric pressure when one end of the tube is open to the atmosphere.

1661 Irish chemist Robert Boyle published "The Sceptical Chymist" in which he introduced the concept of elements. At the time only 12 elements had been identified. These included nine metals, Gold, Silver, Copper, Tin, Lead, Zinc, Iron, Antimony and Mercury and two non metals Carbon and Sulphur all of which had been known since antiquity as well as Bismuth which had been discovered in Germany around 1400 A.D.. Platinum had been known to South American Indians from ancient times but only became to the attention of Europeans in the eighteenth century. Boyle himself discovered phosphorus which he extracted from urine in 1680 taking the total of known elements to fourteen.

Though an alchemist himself, believing in the possibility of transmutation of metals, he was one of the first to break with the alchemist's tradition of secrecy and published the details of his experimental work including failed experiments.

1662 Boyle published Boyle's Law stating that the pressure and volume of a gas are inversely proportional.

The relationship was also discovered by the French physicist Edme Mariotte in 1676 and is known by his name in non-English speaking countries.

1663 Otto van Guericke the Burgomaster of Magdeburg in Germany invented the first electric generator, which produced static electricity by rubbing a pad against a large rotating sulphur ball. The first machine to produce an electric spark and remained the standard way of producing electricity for over a century. Van Guericke was famed for his studies of the properties of a vacuum and for his design of the Magdeburg Hemispheres experiment.

1665 Boyle published a description of a hydrometer for measuring the density of liquids which was essentially the same as those still in use today for measuring the specific gravity (S.G.) of the electrolyte in Lead Acid batteries. Hydrometers consist of a sealed capsule of lead or mercury inside a glass tube into which the liquid being measured is placed. The height at which the capsule floats represents the density of the liquid.

The hydrometer, called the aerometer by the Greeks, is however considered to be the invention of Hypatia head of the Platonist school at Alexandria in about 400 A.D. where she lectured on mathematics and philosophy. Unfortunately she was killed by a Christian mob who at the time equated science with paganism.

1675 Boyle discovered that electric force could be transmitted through a vacuum and observed attraction and repulsion.

1676 Prolific English engineer, surveyor, architect, physicist, inventor, socialite and self publicist, Robert Hooke, is now mostly remembered for for Hooke's Law for springs which states that the extension of a spring is proportional to the force applied, or as he wrote it in Latin "Ut tensio, sic vis" ("as is the extension, so is the force"). From this the energy stored in the spring can be calculated by integrating the force times the displacement over the extension of the spring. The force per unit extension is known as the spring constant. Hooke actually discovered his law in 1660, but afraid that he would be scooped by his rival Newton, he published his preliminary ideas as an anagram "ceiiinosssttuv" in order to register his claim for priority. It was not until 1676 that he revealed the law itself. The forerunner of digital time stamping?

Hooke was surveyor of the City of London and assistant to Christopher Wren in rebuilding the city after the great fire of 1666. He made valuable contributions to optics, microscopy, astronomy, the design of clocks, the theories of springs and gases, the classification of fossils, meteorology, navigation, music, mechanical theory and inventions, but despite his many achievements he was overshadowed by his contemporary Newton with whom he was unfortunately, constantly in dispute. Hooke claimed a role in some of Newton's discoveries but he was never able to back up his theories with mathematical proofs. Apparently there was at least one subject which he had not mastered.

1679 German mathematician, diplomat and philosopher Gottfried Wilhelm Leibniz introduced binary arithmetic in a letter written to French mathematician and Jesuit missionary to China, Joachim Bouvet, showing that any number may be expressed by 0's and 1's only. Now the basis of digital logic and signal processing used in computers and communications.

Surprisingly Leibniz also suggested that God may be represented by unity, and "nothing" by zero, and that God created everything from nothing. He was convinced that the logic of Christianity would help to convert the Chinese to the Christian faith. He believed that he had found an historical precedent for this view in the 64 hexagrams of the Chinese I Ching or the Book of Changes attributed to China's first shaman-king Fuxi (Fu Hsi) dating from around 2800 B.C. and first written down as the now lost manual Zhou Yi in 900 B.C.. A hexagram consists of blocks of six solid or broken lines (or stalks of the Yarrow plant) forming a total of 64 possibilities. The solid lines represent the bright, positive, strong, masculine Yang with active power while the broken or divided lines represent the dark, negative, weak, feminine Yin with passive power. According to the I Ching, the two energies or polarities of the Yin and Yang are both opposing and complementary to eachother and represent all things in the universe which is a progression of contradicting dualities.

Although the I Ching had more to do with fortune telling than with mathematics, there were other precedents to Leibniz's work. The first known description of a binary numeral system was made by Indian mathematician Pingala variously dated between the 5th century B.C. or the 2nd century B.C..

Between the years 1673 and 1686 Leibniz developed the his theories of mathematical calculus publishing the first account of differential calculus in 1684 followed by the explanation of integral calculus in 1686. Unknown to him these techniques were also being developed independently by Newton and arguments about priority raged for many years after both men published their works. Leibniz's notation has been adopted in preference to Newton's but the concepts are the same.

Leibniz also introduced the words function, variable, constant, parameter and coordinates to explain his techniques.

His most famous philosophical proposition was that God created "the best of all possible worlds".

1681 French physicist and inventor Denis Papin invented the pressure release valve or safety valve to prevent explosions in pressure vessels. Although Papin is credited with the invention, safety valves had in fact been described by Glauber thirty years earlier, however Papin's valve was adjustable for different pressures by means of moving the lead weight along a lever which kept the valve shut. The invention of the safety valve came as a result of his work with pressurised steam. In 1679 he had invented the pressure cooker which he called the steam digester. Observing that the steam tended to lift the lid of his cooker in 1690 he conceived the idea of using the pressure of steam to drive a piston in a cylinder to perform a pumping action, the genesis of the steam engine. In 1707 Papin used his safety valve as a regulating device on a steam engine which he had built. Thereafter, it became a standard feature on steam engines saving many lives from explosions.

1687 "Philosophiae Naturalis Principia Mathematica" - Mathematical Principles of Natural Philosophy published by English physicist and mathematician Isaac Newton. One of the most important and influential books ever published, it was written in Latin and not translated into English until 1729.

He made significant advances in the study of Optics demonstrating that white light is made up from the spectrum of colours observed in the rainbow. He used a prism to separate white light into its constituent colour spectrum and by means od a second prism he showed that the colours could be recombined into white light.

He is perhaps best remembered however for his Mechanics, the Laws of Motion and Gravitation which his "Principia" contains. The concept of gravity was completely new. Before that, planetary motion had been explained by Gilbert as well as his contemporary the German astronomer Kepler (1571-1630), and others as being due to magnetic forces.

Newton's first law of motion that "every body remains in a state of rest or uniform motion in a straight line unless compelled to change by some external force" is however a restatement of Galileo's concept of inertia or resistance to change which is measured by its mass.

The impact of the publication of Newton's laws of dynamics on the scientific community was both profound and wide ranging. The laws and Newton's methods provided the basis on which other theories, such as fluid dynamics, kinetic energy and work done were built and down to earth technical knowledge which enabled the building of the machines to power the Industrial Revolution and, at the other end of the spectrum, they explained the workings of the Universe.

However, of equal or even greater importance was the fact that Newton showed for the first time, the general principle that natural phenomena, events and time varying processes, not just mechanical motions, obey laws that can be represented by mathematical equations enabling analysis and predictions to be made. The laws of nature represented by the laws of mathematics, the foundation of modern science. The 3 volume publication was thus a major turning point in the development of scientific thought, sweeping away superstition and so called "rational deduction" as ways of explaining the wonders of nature. Newton's reasoning was supported by his invention of the mathematical techniques of Differential and Integral Calculus and Differential Equations, actually developed in 1665 and 1666, twenty years before he wrote the "Principia" but not used in the proofs it contains. These were major advances in scientific knowledge and capability which extended the range of existing mathematical tools available for characterising nature and for carrying out scientific analysis.

Newton engaged in a prolonged feud with Robert Hooke who claimed priority on some of Newton's ideas. Newton's oft repeated quotation "If I have seen further, it is by standing on the shoulders of giants." was actually written in a sarcastic letter to Hooke, who was almost short enough to be classified as a dwarf, with the implication that Hooke didn't qualify as one of the giants.

Leibniz working contemporaneously with Newton also developed techniques of differential and integral calculus and a dispute developed with Newton as to who was the true originator. Newton's discovery was made first, but Leibniz published his work before Newton. However there is no doubt that both men came to the ideas independently. Newton developed his concept through a study of tangents to a curve and also considered variables changing with time, while Leibniz arrived at his conclusions from calculations of the areas under curves and thought of variables x, y as ranging over sequences of infinitely close values.

Newton is revered as the founder of modern physical science, but despite the great fame he achieved in his lifetime, he remained a modest, diffident, private and religious man of simple tastes. He never married, devoting his life to science.

Newton didn't always have his head in the clouds. In his spare time, when he wasn't dodging apples, he invented the cat-flap.

1705 English physicist and instrument maker Francis Hauksbee the Elder demonstrated an electroluminescent glow discharge lamp which gave off enough light to read by. It was based on van Guericke's electric generator with an evacuated glass globe, containing mercury, replacing the sulphur ball. It produced a glow when he rubbed the spinning globe with his bare hands.

1713 Prolific French scientist and entomologist René-Antoine Ferchault de Réaumur invents spun glass fibres. In an attempt to make artificial feathers from glass he made fibres by rotating a wheel through a pool of molten glass, pulling out threads of glass where the hot, thick liquid stuck to the wheel. His fibers were short and fragile, but he predicted that spun glass fibers as thin as spider silk would be flexible and could be woven into fabric.

In 1731 Réaumur also invented an alcohol thermometer and a corresponding temperature scale which both bear his name. The temperature scale assigned zero degrees to the freezing point of water and eighty degrees its boiling point. The freezing point was fixed and the tube graduated into degrees each of which was one-thousandth of the volume contained by the bulb and tube up to the zero mark. It was an accident dependent on the expansion of the particular quality of alcohol employed which made the boiling point of water 80 degrees.

1714 The first mercury thermometer was made by Polish inventor Gabriel Fahrenheit. It had improved accuracy over the alcohol thermometer due to the more predictable expansion of mercury combined with improved glassworking techniques. At the same time Fahrenheit introduced a standard temperature scale based on the two fixed points of the freezing and boiling points of water.

1725 French weaver Basile Bouchon used a perforated paper roll in a weaving loom to establish the pattern to be reproduced in the cloth. The world's first use of manufacturing automation by using a stored program to control an automated machine.

1728 Another French weaver, Jean Falcon worked with Bouchon to improve his design by changing the perforated paper roll to a chain of more robust punched cards to enable the program to be changed more quickly.

1729 English chemist Stephen Gray was the first to identify the phenomenon of electric conduction and the properties of conductors and insulators and the first to transmit electricity over a wire. He sent charges nearly 300 feet over brass wire and moistened thread and showed that electricity doesn't have to be made in place by rubbing but can also be transferred from place to place with conducting wire. An electrostatic generator powered his experiments, one charge at a time. The fore-runner to the electric telegraph.

1733 French soldier, diplomat and chemist Charles-Francois de Cisternay du Fay discovered two types of electrical charge, positive and negative which he called "vitreous" and "resinous" from the materials used to generate the charge.

1738 Swiss mathematician Daniel Bernoulli showed that Newtons Laws apply to fluids as well as solids and that as the velocity of a fluid increases, the pressure decreases, a statement known as the Bernoulli principle.

More generally the Bernoulli Equation is a statement of the conservation of energy in a form useful for solving problems involving fluid mechanics or fluid flow. For a non-viscous, incompressible fluid in steady flow, the sum of pressure, potential and kinetic energies per unit volume is constant at any point.

Bernoulli's equation also underpins the theory of flight. Lift is created because air passing over the top of the wing must travel further and hence faster that air travelling the shorter distance under the wing. This results in a lower pressure above the wing than below the wing and this pressure difference creates the lift.

Daniel Bernoulli was also the first to explain that the pressure exerted by a gas on the walls of its container is the sum of the many collisions by individual molecules, all moving independently of each other - the basis of the gas laws and the modern kinetic theory of gases.

Daniel Bernoulli was a member of a family of Bernoullis many of whom gained international distinction in mathematics. They were Calvinists of Dutch origin but were driven from Holland by religious persecution finally settling at Basel in Switzerland.

James (Jacques/Jakob) Bernoulli was the first to come to prominence. He learned about calculus from Leibniz and was one of the first users and promoters of the technique. In his Ars Conjectandi, "The Conjectural Arts" published in 1713, eight years after his death by his nephew Nicholas Bernoulli, he established the principles of the calculus of probabilities - the foundation of probability theory as well as the principles of permutations and combinations. He was also one of the first to use polar coordinates.

John (Jean/Johann) Bernoulli, James' brother and father of Daniel was clever but unscrupulous, fraudulently substituting the work of his brother James, of whom he was jealous, for his own to cover up his errors. He also banished his son Daniel from his home when he was awarded an prize he himself had expected to win. Nevertheless he was a great teacher an advanced the theory of calculus to explore the properties of exponential and other functions.

John's three sons Nicholas, Daniel and John Bernoulli the younger and his two sons John and James all achieved distinction in mathematics in their own right.

1744 Prolific French inventor Jacques de Vaucanson maker of robot devices and automatons playing musical instruments and imitating the movements of birds and animals, turned his attention to the problems of mechanisation of silk weaving. Building on the inventions of Bouchon and Falcon, he built a fully automated loom which used perforated cards to control the weaving of patterns in the cloth. Vaucanson also invented many machine tools and collected others which became the foundation of the 1794 Conservatoire des Arts et Métiers (Conservatory of Arts and Trades) collection in Paris. Although Vaucanson's loom was ignored during his lifetime, it was rediscovered more than a half century later at the Conservatoire by Jacquard who used it as the basis for his own improved design.

1745 Electricity first stored in a bottle (literally). The discovery of the Leyden Jar, essentially a large capacitor, was claimed by various experimenters but generally attributed to a Dutch physicist and mathematician Pieter van Musschenbroek and his student Andreas Cunaeus (whom he almost electrocuted with it) working at Leyden in Holland. The first source of stored electrical energy the Leyden jar was simply a jar filled with water, with metal foil around the outside and a nail piercing the stopper and dipping into the water.

A similar device was also invented at the same time by Ewald Jurgens von Kleist Dean of the Cathedral of Kammin in Germany.

The design was improved in 1747 by English astronomer John Bevis who replaced the water with an inner metal coating covering the bottom and sides nearly to the neck. A brass rod terminating in an external knob passed through a wooden stopper or cork and was connected to the inner coating by a loose chain or wire.

Until the advent of the battery, Leyden jars and electrostatic generators were the experimenters' only source of electrical energy. They were however not only made for scientific research, but also as curiosities for amusement. In the 18th century, everybody who had heard of it wanted to experience an electric shock. Experiments like the "electric kiss" were a salon pastime.

1746 French clergyman and physicist Jean Antoine Nollet demonstrated that electricity could be transmitted instantaneously over great distances suggesting that communications could be sent by electricity much faster than a human messenger could carry them.

With the connivance of the Abbot of the Grand Convent of the Carthusians in Paris he assembled 200 monks in a long snaking line with each monk holding the ends of eight metre long wires to form a chain about one mile long. Without warning he connected a Leyden Jar to the ends of the line giving the unsuspecting monks a powerful electric shock and noted with satisfaction that all the monks started swearing and contorting, reacting simultaneously to the shock. A second demonstration was performed at Versailles for King Louis XV, this time by sending current through a chain of 180 Royal Guards since by now the monks were less than cooperative. The King was both impressed and amused as the soldiers all jumped simultaneously when the circuit was completed.

1747 - 1753 Wealthy, eccentric English loner Henry Cavendish discovered the concept of electric potential, that the Inverse Square Law applied to the force between electric charges, that the capacity of a condenser depends on the substance between the plates (the dielectric) and that the potential across a conductor is proportional to the current through it (Ohm's Law).

Charge was provided by Leyden Jars. Potential was "measured" by observing the deflection of the two gold leaves of an electrometer but since no instruments for the measurement of electric current existed at the time, Cavendish simply shocked himself, and estimated the current on the basis of the extent and magnitude of the resulting pain.

Cavendish recorded all his experiments in notebooks and manuscripts but published very little, principally the results of the chemical experiments which formed the bulk of his work. It was therefore left to Coulomb (1785), Ohm (1827) and Faraday (1837) to rediscover these laws many years afterwards. His papers were discovered over a century later by James Clerk Maxwell who annotated and published them in 1879.

Cavendish's family endowed the Cambridge University Cavendish Laboratories at which many of the world's discoveries in the field of nuclear physics were made.

1747 British physicist Sir William Watson, Bishop of Landaff, ran a wire on insulators across Westminster Bridge over the Thames to a point across the river over 12,000 feet away. Using an earth or ground return through the river. He was able to send a charge sufficiently intense after passing through three people to ignite spirits of wine. Watson was probably the first man to use ground conduction of electricity, though he may not have been aware of its significance at the time. Watson was the first to recognise that a discharge of static electricity is equivalent to an electric current.

1748 Watson uses an electrostatic machine and a vacuum pump to make a glow discharge lamp. His glass vessel was three feet long and three inches in diameter. The first fluorescent light bulb.

1748 To carry out measurements with less risk of electrocution of the experimenter or dragooned assistants Nollet invented one of the first electrometers, the electroscope, which detected the presence of electric charge by using electrostatic attraction and repulsion between two pieces of metallic foil, usually gold leaf, mounted on a conducting rod which is insulated from its surroundings. The first voltmeters.

1750 Nollet demonstrated the astonishing efficiency of electrostatic spraying, an idea which was not put to practical use until it was rediscovered by Ransburg in 1941.

1750 English physicist John Michell describes magnetic induction, the production of magnetic properties in unmagnetised iron or other ferromagnetic material when it is brought close to a magnet. He discovered that the two poles of a magnet are of equal strength and that they obey the inverse-square law for magnetic attraction in "A Treatise on Artificial Magnets".

1752 French experimenter Thomas François Dalibard, assisted by retired illiterate old dragoon M. Coiffier, carried out an experiment proposed by Benjamin Franklin. From a safe distance (in Dalibard's case eighteen miles away) they used a long pointed iron rod, insulated from the ground by glass bottles, to attract a lightning discharge from a thunder cloud. Coiffier subsequently drew electrical sparks from the charged rod to prove that thunder clouds contain electricity and that it can be conducted down a metal rod.

1752 Johann Georg Sulzer notices a tingling sensation when he puts two dissimilar metals, just touching eachother, on either side of his tongue. It became known later as the battery tongue test: - the saliva acting as the electrolyte carrying the current between the two metallic electrodes.

1752 A man of many talents, Benjamin Franklin one of the leaders of the American Revolution and founding fathers of the USA, journalist, publisher, author, philanthropist, abolitionist, public servant, scientist, diplomat and inventor carried out his kite experiments in 1752, one month after Dalibard, and invented the lightning rod. He proposed a "fluid" theory of electricity and outlined the concepts of positive and negative charges, current flow and conductors coining the language to describe them. Words such as battery (from an array of charged glass plates, and later, a number of Leyden Jars), charge, condenser (capacitor), conductor, plus, minus, positively, negatively, armature, electric shock and electrician which we still use today.

Whilst it may be heresy to suggest that Franklin did not carry out the kite experiment for which he is famous, there are no reliable witnesses to this event and it is a fact that nobody, including Franklin, has yet been able to duplicate this experiment in the manner he described, and few have been willing to try. One who did was Professor Georg W Richmann a Swedish physicist working in St Petersburg who was killed in the attempt on 6 August 1753. He was the first known victim of high voltage experiments in the history of physics. Benjamin Franklin was lucky not to win this honour.

1753 A proposal is submitted in an anonymous letter to the Scotsman Magazine signed "C.M.", generally attributed to Scottish surgeon Charles Morrison, for 'An Expeditious Method of Conveying Intelligence'. It described an electrostatic telegraph system using 26 insulated wires to conduct separate charges from a Leyden Jar causing movements in small pieces of paper on which each letter of the alphabet is written.

1757 French botanist Michel Adanson proposed that the discharge from the Senegalese (electric) catfish could be compared with the discharge from a Leyden jar. The ability of certain torpedo fish or sting rays to inflict electric shocks had been known since antiquity however Adanson's theory was new. It was later proved by British administrator and M.P., John Walsh, secretary to Clive of India, who in 1772 managed to draw a spark from an electric eel. It is quite possible that news of Walsh's experiment influenced Galvani to begin his own experiments with frogs.

1759 German mathematician Franz Maria Ulrich Theodosius Aepinus published his book, An Attempt at a Theory of Electricity and Magnetism. The first work to apply mathematics to the theory of electricity and magnetism, it explained most of the then known phenomena.

In 1889 Aepinus also made the first variable capacitor which he used to investigate the properties of dielectrics. It had flat plates which could be moved apart and different materials could be inserted between them. Volta also laid claim to the invention of this device and to giving it the name of "capacitor".

1761 Scottish chemist and physicist Joseph Black working at Glasgow University, discovered that ice absorbs heat without changing temperature when melting. Between 1759 and 1763 he evolved the theory of latent heat for a heat flow that results in no change of temperature, that is, for the heat flows which accompany phase transitions such as boiling or freezing. He also showed that different substances have different specific heats, the amount of heat per unit mass required to raise its temperature by one degree Celsius.

1766 Swiss physicist, geologist and early Alpine explorer Horace Benedict de Saussure invents the first true electrometer for measuring electric potential by means of attraction or repulsion of charged bodies. It consisted of two pith balls suspended by separate strings inside an inverted glass jar with a printed scale so that the distance or angle between the balls could be measured. It was de Saussure who discovered the distance between the balls was not linearly related to the amount of charge.

1767 English clergyman, philosopher and social reformer Joseph Priestley at the age of 34 made his first foray into the world of science with the publication of a two-volume History of Electricity in which he argued that the history of science was important since it could show how human intelligence discovers and directs the forces of nature. The previous year in London he had met Benjamin Franklin who introduced him to the wonders of electricity and they became lifelong friends. Priestley's first discovery, also in 1767, was that carbon conducts electricity.

Though he had no scientific training, Priestley is however better known as a chemist. He isolated Carbon dioxide, which he called "fixed air", and in a paper published in 1772, he showed that a pleasant drink could be made by dissolving the gas in water. Thus was born carbonated (soda) water, the basis of the modern soft drinks industry.

He was a great experimenter discovering Nitrous oxide (laughing gas) and several other chemical compounds and unaware of the work of Scheele he independently discovered Oxygen. Priestley was no theorist however and he passed on his results to the French chemist Lavoisier who repeated the experiments taking meticulous measurements in search of underlying patterns and laws governing the chemical reactions.

Experimenting with growing plants in an atmosphere of Carbon dioxide, Priestley observed that the plants consumed the Carbon dioxide and produced Oxygen, identifying the process of plant respiration and photosynthesis. This was the first connection between chemistry and biology.

As a reformer, Priestley was a strong supporter of the 1776 American and the 1789 French Revolutions. This brought him into conflict with conservatives and in 1791 angry mobs burnt down his house and his church destroying many of his manuscripts. The intimidation continued until 1794 when the aristocratic Lavoisier, on the opposite side of the revolutionary fence from Priestley, was executed by French revolutionaries. A few weeks later Priestley emigrated to America to escape persecution spending the rest of his life there.

1769 The large scale generation of electricity could never have happened without James Watt's steam engine which for many years, apart from a few hydroelectric schemes, was the prime mover for driving electric generators. Starting in 1769 Watt made a series of improvements to the steam engine originally patented in 1698 by the English engineer Thomas Savery in and improved by Thomas Newcomen in 1712. Watt's major contribution was the addition of a separate condenser, for condensing the steam, that could be kept cool while the working cylinder remained hot, thus reducing heat losses on every cycle and improving the efficiency of the machine. The introduction of Watt's steam engine was a key event in the Industrial Revolution.

1771 The world's first machine powered factory began operations in Cromford, Derbyshire. English inventor Richard Arkwright pioneered large scale manufacturing using a water wheel to replace manual labour used to power the spinning frames in his cotton mill.

1774 An electrostatic telegraph is demonstrated in Geneva, Switzerland by Frenchman George Louis LeSage. He built a device composed of 24 wires each contained in a glass tube to insulate the wires from eachother. At the end of each wire was a pith ball which was repelled when a current was initiated on that particular wire. Each wire stood for a different letter of the alphabet. When a particular pith ball moved, it represented the transmission of the corresponding letter. Intelligible messages were transmitted over short distances and LeSage's system is considered to be the first serious attempt at making an electrical telegraph.

1775 Like many experimenters of his time Alessandro Volta constructed his own Perpetual Electrophorus (that which carries off electricity) to provide a regular source of electricity for his experiments. It was crude and consisted of a resin plate on which was rubbed cat's fur or a fox tail and another insulated metal plate for picking up the charge.

1775 In response to the demands of the armaments industry the nascent steam power industry English engineer John Wilkinson made one of the first precision machine tools, a cylinder boring machine. His machine secured for him the largest share in the profitable business of supplying cannons in the American War of Independence. Wilkinson is reputed to be Britain's first industrialist to become a millionaire.

1782 French mathematician Pierre-Simon Laplace, building on earlier work by Swiss mathematician Leonhard Euler, develops a mathematical operation now called the Laplace Transform as a tool for solving linear differential equations. The most significant advantage is that differentiation and integration become multiplication and division, respectively. This is similar to the way that logarithms change an operation of multiplication of numbers into the simpler addition of their logarithms. By applying Laplace's integral transform to each individual term in differential equations, the terms can be rewritten in terms of a new variable "s" and the equations are converted into polynomial equations which are much easier to solve by simple algebra. The solutions to the original problems are retrieved by applying the Inverse Laplace Transform.

This technique simplifies the analysis control systems and analogue circuits which are characterised by time varying differential equations. Laplace's method thus transforms differential equations in the time domain into algebraic equations in the s-domain.

Between 1799 and 1825 Laplace published in five volumes "Traité de Mécanique Céleste", Celestial Mechanics, in which he translated the geometrical study of mechanics used by Newton to one based on calculus.

Laplace also developed the foundations of probability theory which he published in 1812 as "Théorie Analytique des Probabilités". Prior to that, probability theory was solely concerned with developing a mathematical analysis of games of chance. Laplace applied the theory to the analysis of many practical problems in the social, medical, and juridical fields as well as in the physical sciences including mortality, actuarial mathematics, insurance risks, the theory of errors, statistical mechanics and the drawing of statistical inferences.

In 1799 Laplace was appointed by Napoleon as Minister of the Interior but he was removed after only six weeks "because he brought the spirit of the infinitely small into the government".

1784 Cavendish demonstrated that water is produced when hydrogen burns in air, thus proving that water is a compound of two gases and not an element and overturning over two thousand years of conventional wisdom.

1784 King Louis XVI of France set up a Royal Commission to evaluate the claims by German healer and specialist in diseases of the wealthy, Franz Anton Mesmer who had achieved international notoriety with his theory animal magnetism and its supposed therapeutic powers. Members of the committee included Benjamin Franklin, Antoine Lavoisier and the physician Joseph-Ignace Guillotin, inventor of the Guillotine which was later used to remove the heads of both Lavoisier and the King. Mesmer had claimed extraordinary powers to cure patients of various ailments by using magnets. He also claimed to be able to magnetise virtually anything including paper, wood, leather, water, even the patients themselves and that he himself was a source of animal magnetism, a magnetic personality. His clients were mainly aristocratic women many of whom reported pleasurable experiences as Mesmer moved his hands around their bodies to align the flow of magnetic fluid while they were in a trance. Mesmer was a patron of the composer Wolfgang Amadeus Mozart who included a scene in which Mesmer's magnets were used to revive victims of poisoning in the opera "Cosi fan tutte". The committee however concluded that all Mesmer's observed effects could be attributed to the power of suggestion and he was denounced as a fraud. He did however keep his head (the French revolution was still four years away) and his name lives on as hypnotists mesmerise their subjects.

Guillotin by the way was not a revolutionary. As a physician he merely proposed the guillotine as a more humane method of execution rather than hacking away with a sword.

1785 French military engineer and physicist, Charles-Augustin de Coulomb published the correct quantitative description of the force between electrical charges, the Inverse Square Law, which he verified using a sensitive torsion balance which he had invented in 1777. He showed that the electrical charge is on the surface of the charged body. Coulomb's Law was the first quantitative law in the history of electricity.

1786 Luigi Galvani professor of anatomy at Bologna Academy of Science in Italy discovered that two dissimilar metals applied to the leg of a dead frog would make it twitch although he believed that the source of the electricity was in the frog. He was quite possibly influenced in his conclusions by the knowledge of Walsh's experiments with electric fish. Could it be animal electricity?. He found copper and zinc to be very effective in making the muscles twitch. His friend Volta on the other hand believed the electricity came from the metals and for many years a debate raged until it was eventually resolved by Volta's invention of the Voltaic pile. In the meantime Galvani lost his job for refusing to swear allegiance to Napoleon's Cisalpine Republic whereas Volta attempted to accommodate Napoleon and prospered under his rule. Sadly Galvani died in 1798 without knowing the outcome of the debate.

1787 Experiments by French physicist and chemist Jacques Charles (later continued by Joseph Louis Gay-Lussac) revealed that:

This work provided the inspiration for Kelvin's subsequent theories on thermodynamics.

Charles' Law and Gay Lussac's Law together with Boyle's Law are known collectively as the Gas Laws.

In his spare time, Charles was an enthusiastic balloonist making several ascents and improving ballooning equipment.

1789 French chemist Antoine Laurent Lavoisier considered to be the founder of modern chemical science, published Traité Élémentaire de Chimie or "Elementary Treatise of Chemistry", the first modern chemistry textbook. In it he presented a unified view of new theories of chemistry and a clear statement of the Law of Conservation of Mass which he had established in 1772. In addition, he defined elements as substances which could not be broken down further and listed all known elements at the time including oxygen, nitrogen, hydrogen, phosphorus, mercury, zinc, and sulphur. As intended, it did for chemistry what Newton's Principia had done for physics one hundred years earlier.

Lavoisier was the first to apply rigorous scientific method to chemistry. He carried out his experiments on chemical reactions with meticulous precision devising closed systems to ensure that all the products of the reactions were measured and accounted for. He thus demolished the wild ideas of the alchemists as well as the Greek concept of four elements, earth, air, fire and water which had been accepted for over 2000 years.

Lavoisier had a wide range of interests and a prodigious appetite for work and funded his experiments from his part time job as a tax collector. He was aided in his scientific endeavours by his wife Marie-Anne Pierrette Paulze, whom he had married when she was only thirteen years old. The couple were at the centre of a Parisian social life, but in 1794 Lavoisier's tax collecting activities fell foul of France's revolutionary mob and he was Guillotined during the Reign of Terror. An appeal to spare his life was cut short by the judge with the words "The Republic has no need of scientists".

Afterwards the French mathematician Joseph-Louis Lagrange said "It took them only an instant to cut off that head, and a hundred years may not produce another like it".

1790 The first patent laws established un the USA by a group led by Thomas Jefferson. Until US Independence, when Intellectual Property Rights were protected by the American Constitution, the King of England officially owned the intellectual property created by the colonists. Patents had however been issued by the colonial governments and were protected by British law.

The first US patent was granted to Samuel Hopkins of Vermont for a new method of making Potash.

1791 German chemist and mathematician Jeremias Benjamin Richter attempted to prove that chemistry could be explained by mathematical relationships. He showed that such a relationship applied when acids and bases neutralize to produce salts they do so in fixed proportions. Thus he was the first to establish the basis of quantitative chemical analysis which he named stoichiometry. He died of tuberculosis at the age of 45.

1795 The hydraulic press used for metal forming invented by English engineer Joseph Bramah.

1797 Young Prussian noble Alexander von Humboldt published a book outlining his theories about Galvanic electricity and his experiments to support them. He believed that the electricity came from the muscle and was intensified by the electrodes and he carried out experiments on plants and animals to prove it. He also carried out numerous experiments on himself to gather more data using a Leyden jar to inflict severe shocks on his body until it was badly lacerated and scarred. He was mortified three years later when his theories were proved completely wrong by Volta and turned his attention instead to geology, botany and exploration in all of which he found international fame but no fortune.

1797 English engineer Henry Maudslay introduced the precision screw-cutting lathe. Although lathes had been in use from before 3000 B.C. when the Egyptians used the bow lathe for wood turning, Maudslay's lathe was the first true ancestor of the modern machine tools industry. He raised the standards of precision, fits, finishes and metrology and invented the first bench micrometer capable of measuring to one ten thousandth of an inch which he called the "Lord Chancellor" because it resolved disputes about the accuracy of workmanship in his factory.

Maudslay's pupils included Scottish engineer James Naysmith who designed and made heavy machine tools, including the shaper and the steam hammer, for the ship building and railway industries and English engineer Joseph Whitworth who worked on Babbage's Difference Engine and later introduced the Whitworth standard system for screw-cutting threads which was first adopted by the railways and the Woolwich Arsenal and then became an industry standard enabling interchangeability of components and production automation. See also Whitney - next.

1798 In an age when mechanical devices were individually made and laboriously fitted by hand, American engineer Eli Whitney pioneered the concept of interchangeable parts in the USA, using precision manufacturing made possible by more accurate machine tools just becoming available. Prior to that, if a part failed, a replacement part had to be made and fitted individually creating major problems and losses in battlefield conditions. Whitney's methods also reduced the skill levels needed to manufacture and assemble the parts enabling him to take on a contract to supply 10,000 muskets in two years to the US government. Whitney also built a rudimentary milling machine in 1818 for use in firearms manufacturing, but the universal milling machine as we would recognise it today was invented by American engineer Joseph Rogers Brown in 1862. Brown's machine was able to cut the flutes in twist drills. Since the introduction of twist drills in the 1820's these flutes had been filed by hand.

1799 Count Rumford, man of science, inventor, administrator, philanthropist, self publicist and scoundrel, born Benjamin Thompson in the USA, founded The Royal Institution in London to promote and disseminate the new found knowledge of the industrial revolution. Its first director was a well connected, glamorous young Cornish chemist, Humphry Davy. Davy was a great showman, but did not consider "common mechanics" worthy of his brilliance, so the Institution rapidly evolved to presenting lectures for the wealthy, who paid to attend. In Rumford's original plan, there had been a back door through which the poor could access a balcony to hear the lectures from a distance for free. Davy had it bricked up. The Institution did, however, perform a very valuable function in that it was a subsidised science lab, one of the very few in the world, which enabled scientists of the day, such as Michael Faraday, to make many important discoveries.

Rumford was a colourful character, like fellow American Benjamin Franklin, a man of many talents. Raised in pre-Revolutionary New England, at the age of 19 he married a wealthy 31-year-old widow and he took up spying on the colonies for the British but left for England in 1776 when he was found out, deserting his wife and daughter. At first he worked in the British foreign office as undersecretary for Colonial Affairs and was knighted by George III after a stint in the army fighting on the British side in the American War of Independence. He moved on to Munich where he carried out public and military works for the Elector of Bavaria being rewarded in 1792 with the title Count of the Holy Roman Empire. Among his inventions were the drip coffee pot and thermal underwear.

His interest in field artillery led him to study both the boring and firing of cannons. Out of this work he saw that mechanical power could be converted to heat -- that there was a direct equivalence between thermal energy and mechanical work. Heat was produced by friction in unlimited quantities so long as the work continued. It could therefore not be a fluid called a Caloric flowing in and out of a substance as his adversary, the noted French chemist, Antoine Lavoisier, had proposed, since the fluid would have a finite quantity.

After Lavoisier's death Rumford started a four year affair with his wealthy, young widow, however after a short unhappy marriage they divorced with Rumford remarking that Lavoisier was lucky to have been guillotined. Rumford lived out the rest of his life in Lavoisier's former house in France engaged in scientific studies and it is claimed that he was paid by the French for spying on the British.

VOLTA

Alessandro Volta

Thee man who started it all.

Voltaic pile

Volta's Pile

Alessandro Volta of the University of Pavia, Italy, describes the principle of the electrochemical battery in a letter to the Royal Society in London. The first device to produce continuous electric current. He had been interested in electrical phenomena since 1763 and in 1775 he had made his own electrophorus for carrying out his experiments. He was a friend of Galvani but disagreed with him about the nature of electricity. Galvani's experiments with frogs had led him to believe that the source of the electricity was the frog, however Volta sought to prove that the electricity came from the dissimilar metals used to probe the specimen.

His "Voltaic Pile" was initially presented in 1800 as an "artificial electric organ" to demonstrate that the electricity was independent of the frog. It was constructed from pairs of dissimilar metals zinc and silver separated by a fibrous diaphragm (Cardboard?) moistened with sodium hydroxide or brine and provided the world's first continuous electric current. The pile produced a voltage of between one and two volts. To produce a higher voltages he connected several piles together with metal strips to form a "battery". He was the first to understand the importance of "closing the circuit".

Volta's invention caused great excitement at the time and he gave many demonstrations including drawing sparks from the pile, melting a steel wire (the first fuse?), discharging an electric pistol and decomposing water into its elements. Napoleon was particularly impressed, insisting on helping with the demonstrations when he was present and showering Volta with honours despite the fact that France and Italy were initially at war with each other. The unit of electric potential was named the Volt in his honour.

After the invention of the battery, Volta was awarded a pension by Napoleon and he began to devote more of his time to politics, holding various public offices. He retired in 1819 and died in 1827 and although the battery was a sensation in scientific circles and giving impetus to an intensification of scientific investigation and discovery throughout the nineteenth century, surprisingly Volta himself never participated in these opportunities.

1800 English scientists, William Nicholson and Anthony Carlisle, experimenting with Volta's chemical battery, accidentally discovered electrolysis, the process in which an electric current produces a chemical reaction, and initiated the science of electrochemistry. (A discovery like many others claimed by Humphry Davy though he did actually do original work at a later date on electrolysis).

This new technique, made possible by the availability of the constant electric current provided by the new found batteries, enabled many compounds to be separated into their constituent elements and led to the discovery and isolation of many previously unknown chemical elements. Electrolysis, "loosening with electricity", thus became widely used by scientific experimenters.

1801 French silk-weaver, Joseph-Marie Jacquard invented an automatic loom using punched cards to control the weaving of the patterns in the fabrics. This was not the earliest implementation of a stored program and the use of punched cards programmed to control a manufacturing process as is often claimed. That honour goes to Bouchon starting in 75 years earlier and improved by Falcon in 1728 and eventually refined by de Vaucanson in 1744. Jacquard presented his invention in Paris in 1804, and was awarded a medal and patent for his design by the French government who consequently claimed the loom to be public property, paying Jacquard a small royalty and a pension. Its introduction caused riots in the streets by workers fearing for their jobs.

Despite the loom's fame, Jacquard's principles of programmed control and automation were not applied to any other manufacturing process for another 145 years when Parsons produced the first numerically controlled machine tools.

1801 Frenchman Nicholas Gautherot observed that when a current from a voltaic battery was sent between two Copper plates immersed in Sulphuric acid, for a short period afterwards the copper plates could drive a current back in the opposite direction. He had inadvertently discovered the rechargeable battery but did not realise its significance. Sixty years later Planté repeated the experiment with Lead plates and the Lead Acid battery was born.

1802 English chemist Dr William Cruikshank designed the first battery capable of mass production. A flooded cell battery constructed from sheets of copper and zinc in a wooden box filled with brine or acid.

Cruikshank also discovered the electrodeposition of copper on the cathodes of copper based electrolytic cells and was able to extract metals from their solutions, the basis modern metal refining and of electroplating, but it was not until 1840 that the commercial potential of the plating process was realised by the Elkingtons.

1803 Johann Wilhelm Ritter, a German physicist, first demonstrated the elements of a rechargeable battery made from layered discs of copper and cardboard soaked in brine. Unfortunately there was no practical way to recharge it other than from a Voltaic Pile and for many years they remained a laboratory curiosity until someone invented a charger. Ritter was one of the first to identify the phenomenon of polarisation in acidic cells. He also repeated Galvani's "frog" experiments with progressively higher voltages on his own body. This was probably the cause of his untimely death at the age of 33.

In 1801 after studying the discovery of infrared radiation the previous year by German born English astronomer, Frederick William Herschel, Ritter discovered the ultraviolet region of the spectrum.

1803 John Dalton a Quaker school teacher working in Manchester resurrects the Greek Democritus' atomic theory that every element is made up from tiny identical particles called atoms, each with a characteristic mass, which can neither be created or destroyed. Dalton showed that elements combine in definite proportions and developed the first list of atomic weights which he first published in 1803 at the Manchester Literary and Philosophical Society and at greater length in book form in 1808.

1804 The Electric telegraph one of the first attempted applications of the new electric battery technology was proposed by Catalan scientist Francisco Salvá. One wire was used for each letter of the alphabet and each number. The presence of a signal was indicated by a stream of hydrogen bubbles when the telegraph wire was immersed in acid. The system had a range of one kilometer.

1805 Italian chemist Luigi Valentino Brugnatelli, friend of Volta demonstrated electroplating by coating a silver medal with gold. He made the medal the cathode in a solution of a salt of gold, and used a plate of gold for the anode. Current was supplied by a Voltaic pile. Brugnatelli's work was however rebuffed by Napoleon Bonaparte which discouraged him from continuing his work on electroplating.

The process later became widely used for rust proofing and for providing decorative coatings on cheaper metals. Gold plating is used extensively today in the electronics industry to provide low resistance, hard wearing, corrosion proof connectors.

1807 English physician, physicist, and Egyptologist Robert Young introduced a measure of the stiffness or elasticity of a material, now called Young's Modulus which relates the deformation of a solid to the force applied. Also called the Modulus of elasticity it can be thought of as the spring constant for solids. Young's modulus is a fundamental property of the material. It enables Hooke's spring constant, and thus the energy stored in the spring to be calculated from a knowledge of the elasticity of the spring material.

Young was the first to assign the term kinetic energy to the quantity ½MV² and to define work done, as force X distance which is also equivalent to energy, an extension to Newton's Laws but surprisingly taking 140 years to emerge. More surprising still is that it was another 44 years before the concept of potential energy was proposed.

He also did valuable work on optical theory and in 1801 he devised the Double slit interference experiment which verified the wave nature of light.

Young is considered by some to be the last person to know everything there was to know. (Not the only candidate to this fame). He was a child prodigy and had read through the Bible twice by the age of four and was reading and writing Latin at six. By the time he was 14 he had a knowledge of at least five languages, and eventually his repertoire grew to 12. He practised medicine until the work load clashed with his other interests, and among his many accomplishments he translated the inscriptions on the Rosetta Stone which was they key which enabled hieroglyphics to be deciphered.

1807 Humphry Davy constructed the largest battery ever built at the time, with over 250 cells, and passed a strong electric current through solutions of various compounds suspected of containing undiscovered elements isolating potassium and sodium by this electrolytic method, followed in 1808 with the isolation of calcium, strontium, barium, and magnesium. The following year Davy used his batteries to create an arc lamp.

In 1813 Davy wrote to the Royal Society stating that he had identified a new element which he called iodine, four days after a similar announcement by Gay-Lussac. The element had in fact been isolated in 1811 from the ashes of burnt seaweed by Bernard Courtois, the son of a French saltpetre manufacturer, who had passed samples to Gay-Lussac and Ampère for investigation. Ampère in turn passed a sample to Davy. Although Courtois discovery was not disputed, both Davy and Gay-Lussac both claimed credit for identifying the element.

1807 As a result of his studies on heat propagation, French mathematician Baron Jean Baptiste Joseph Fourier presented a paper to the Institut de France on the use of simple sinusoids to represent temperature distributions. The paper also claimed that any continuous periodic signal could be represented as the sum of properly chosen sinusoidal waves.

For the previous fifty years the great mathematicians of the day had sought equations to describe the vibration of a taut string anchored at both ends as well as the related problem of the propagation of sound through an elastic medium. French mathematicians Jean d'Alembert and Joseph-Louis Lagrange and Swiss Leonhard Euler and Daniel Bernoulli had already proposed combinations of sinusoids to represent these physical phenomena and in Germany, Carl Friedrich Gauss had also been working on similar ways to analyse mechanical oscillations (see below). Whereas their theories applied to particular situations, Fourier's claim was controversial in that it extended the theory to any continuous periodic waveform.

Among the reviewers of Fourier's paper were Lagrange, Adrien-Marie Legendre and Pierre Simon de Laplace, some of history's most famous mathematicians. While Laplace and the other reviewers voted to publish the paper, Lagrange demurred, insisting that signals with abrupt transitions or "corners", such as square waves could not be represented by smooth sinusoids. The Institut de France bowed to the prestige of Lagrange, and rejected Fourier's work. It was only after Lagrange died that the paper was finally published, some 15 years later.

When Fourier's paper was eventually published in 1822, it was restated and expanded as "Theorie Analytique de la Chaleur", the mathematical theory of heat conduction. The study made important breakthroughs in two areas. In the study of heat flow, Fourier showed that the rate of heat transfer is proportional to the temperature gradient, a new concept at the time, now known as Fourier's Law.

Of greater importance however were the mathematical techniques Fourier developed to calculate the heat flow in unusually shaped objects. He provided the mathematical proof to support his 1807 claim that any repetitive waveform can be approximated by a series of sine and cosine functions, the coefficients of which we now call the Fourier Series. These coefficients represent the magnitudes of the different frequency components which make up the original signal. When the sine and cosine waves of the appropriate frequencies are multiplied by their corresponding coefficients and then added together, the original signal waveform is exactly reconstructed. Thus complex functions such as differential equations can be converted into simpler trigonometric terms which are easier to handle mathematically by calculus or other methods.

This mathematical technique is known as the Fourier transform and its application to an electrical signal or mechanical wave is analogous to the splitting or "dispersion" of a light beam by a prism into the familiar coloured optical spectrum of the light source. An optical spectrum consists of bands of colour corresponding to the various wavelengths (and hence different frequencies) of light waves emitted by the source. In the same way, applying the Fourier transform to an electrical signal separates it into its spectrum of different frequency components, often called harmonics, which makes it very useful in electrical engineering applications.

In electrical engineering applications, the Fourier transform takes a time series representation of a complex waveform and converts it into a frequency spectrum. That is, it transforms a function in the time domain into a series in the frequency domain, thus decomposing a waveform into harmonics of different frequencies, a process which was formerly called harmonic analysis.

The Fourier Transform has wide ranging applications in many branches of science and while many contributed to the field, Fourier is honoured for his insight into the practical usefulness of the mathematical techniques involved.

Fourier led an exciting life. He was a supporter of the Revolution in France but opposed the Reign of Terror which followed bringing him into conflict and danger from both sides. In 1798 he accompanied Napoleon on his invasion of Egypt as scientific advisor but was abandoned there when Nelson destroyed the French fleet in the battle of the Nile. Back in France he later provoked Napoleon's ire by pledging his loyalty to the king after Napoleon's abdication and the fall of Paris to the European coalition forces in 1814. When Napoleon escaped from Elba in 1815 Fourier once more feared for his life. His fears were unfounded however and, despite his disloyalty, Napoleon awarded him a pension but it was never paid since Napoleon was defeated at Waterloo later that year.

As noted above Fourier was not the only one at the time looking for simple solutions to complex mathematical problems. Gauss was trying to calculate the trajectories of the asteroids Pallas and Juno. He knew that they were complex repetitive functions but he only had sampled data of the locations at particular points in time rather than a continuous time varying function from which to construct a mathematical model of the trajectories. Although this was before Fourier's time, like his contemporaries Gauss was aware that the result should be a series of sinusoids, but deriving a transform from sampled or discrete data, rather than from a time varying mathematical function, involves a huge computational task. Such a transform applied to sampled data is now known as a Discrete Fourier Transform (DFT) and can be considered as a digital tool whereas the general Fourier Transform only applies to continuous functions and can be considered as an analogue tool. In 1805 Gauss derived a mathematical short cut for computing the coefficients of his transform. Although he applied it to a specific, rather than a general case, we would recognise Gauss's short cut today as the Fast Fourier Transform (FFT) even though it owed nothing to Fourier.

1808 Prolific Swedish chemist Jöns Jacob Berzelius working at the University of Uppsala in Sweden formulated the Law of Definite Proportions (discovered by Dalton five years earlier and by Richter twelve years before that) which establishes that the elements of inorganic compounds are bound together in definite proportions by weight. Berzelius developed the system of chemical notation we still use today in which the elements were given simple written labels, such as O for oxygen, or Fe for iron, and proportions were noted with numbers. He accurately determined the relative atomic and molecular masses of over 2000 elements and compounds.

1808 Mark Isambard Brunel, father of famous son Isambard Kingdom Brunel, with the task of manufacturing 60,000 wooden pulley blocks per year, set up one of the first ever mass production lines. Instead of one man making a complete pulley Brunel divided the work into a series of simple, short cycle, repetitive tasks and using 43 purpose-built precision machines from Maudslay to carry out the sequential operations in line, he reduced the labour required to do the work from 110 to 10. A formula which has become an industry standard.

1809 Davy produced an electric arc between two carbon electrodes - the first electric light. Davy is generally credited with inventing the carbon arc lamp, however a Russian Vasilli V. Petrov had reported this phenomenon in 1803.

In 1816 Davy claimed the credit for the invention of the miner's safety lamp, named the "Davy lamp" in his honour but it was actually similar to a design already demonstrated in 1815 by self taught railway pioneer George Stephenson. The privileged Davy was incensed that he could be upstaged by working class Stephenson.

According to J. D. Bernal's "Science in History" Davy is quoted as saying "The unequal division of property and of labour, the difference of rank and position amongst mankind, are the sources of power in civilized life, its moving causes, and even its very soul."

1811 Italian physicist Amadeo Avogadro discovered the concept of molecules. He hypothesized that equal volumes of gases at the same temperature and pressure contain equal numbers of molecules. From this hypothesis it followed that relative molecular weights of any two gases are the same as the ratio of the densities of the two gases under the same conditions of temperature and pressure.

The basic scheme of atoms and molecules arrived at by Dalton and Avogadro underpins all modern chemistry.

1812 German physician Samuel Thomas von Sömmering increased the range of Salvás (1804) telegraph to three kilometers by using bigger batteries, a method subsequently used with disastrous results on the Transatlantic Telegraph Cable.

1812 Venetian priest and physicist Giuseppe Zamboni developed the first leak proof high voltage "dry" batteries with terminal voltages of over 2000 Volts. They consisted of thousands of small metallic foil discs of tin or an alloy of copper and zinc called "tombacco", separated by paper discs stacked in glass tubes. The technology was not well understood at the time and while Zamboni consciously avoided the use of any conventional corrosive aqueous electrolyte in the cells, hence the name "dry" battery, the electrolyte was actually provided by the humidity in the paper discs and a variety of experimental greasy acidic pulps spread thinly on the foils to minimise polarisation effects. Although the battery voltage was very high, the internal resistance was thousands of megohms so the current drawn from the batteries was about 10^-9 amps, limiting the battery's potential applications. One notable application however was a primitive electrostatic clock mechanism in which a pendulum was attracted towards the high voltage terminal of a Zamboni pile by the electrostatic force between the pendulum and the terminal. When the pendulum touched the terminal it acquired the same charge as the terminal and was consequently deflected away from it towards the opposite pole of another similar pile from which, by a similar mechanism it was deflected back again, thus maintaining the oscillation. The current drain or discharge rate of the batteries was so low as to be undetectable with instruments available at the time and it was thought that the pendulum was a "perpetual electromotor". In fact Zamboni primary batteries have been known to last for over 50 years before becoming completely discharged!

1813 French mathematician and physicist Siméon Denis Poisson derived the relationship which relates the electric potential in a static electric field to the charge density which gives rise to it. The resulting electric field is equal to the gradient of the potential. This equation describes the electric fields which drive the flow of charged ions through the electrolyte in a battery.

Poisson published many papers during his lifetime but he is perhaps best remembered for his 1837 paper on the statistical distribution now named after him. The Poisson distribution describes the probability that a random event will occur in a time or space interval under the conditions that the probability of the event occurring is very small, but the number of trials is very large so that the event actually occurs only a small number of times. He used his theory to predict the likelihood of being killed by being kicked by a horse and tested it against French army records over several years of the number of soldiers killed in this way. Apart from analysing accident data, the distribution is fundamental to queueing theory which is used in traffic studies to dimension applications from supermarket checkouts and tollgates to telephone exchanges.

1816 A two wire telegraph system based on high voltage static electricity activating pith balls, using synchronous clockwork dials at each end of the channel to identify the letters, was demonstrated in the UK by Francis Ronalds, an English cheese maker and experimental chemist, and subsequently described in his publication of 1823. Coming only a year after Wellington's victory over Napoleon at Waterloo, it was turned down by the haughty Admiralty, who had just invented semaphore signalling, with the comment "Telegraphs of any kind are now wholly unnecessary". It was an invention before its time and nobody showed any interest. At the time it was however witnessed by the young Charles Wheatstone who was later credited in the UK with the invention of the telegraph.

1816 British chemist William Hyde Wollaston built the forerunner of the reserve battery. To avoid strong acids eating away the expensive metal plates of his batteries or cells when not in use, he simply hoisted the plates out of the electrolyte, a system copied by many battery makers in the nineteenth century.

1820 Danish physicist Hans Christian Øersted showed how a wire carrying an electric current can cause a nearby compass needle to move. The first demonstration of the connection between magnetism and electricity and of the existence of a hitherto unknown, non-Newtonian force. Two major scientific discoveries from a simple experiment.

1820 One week after hearing about Øersted's experiment, French physicist and mathematician André-Marie Ampère showed that parallel wires carrying current in the same direction attract eachother, whereas parallel wires carrying current in opposite directions repel eachother.

He also showed that the force of attraction or repulsion is directly proportional to the strength of the current and inversely proportional to the square of the distance between the wires.

He precisely defined the concept of electric potential distinguishing it from electric current. He later went on to develop the relationship between electric currents and magnetic fields.

Ampère's life was not a happy one. Traumatised by his father's execution by the guillotine during the French Revolution, there followed two disastrous marriages, the first one resulting in the early death of his wife. Finally he had to cope with an alcoholic daughter. The epitaph he choose for his gravestone says Tandem Felix ('Happy at last'). The unit of current was named the Ampère in his honour.

1820 French mathematician Jean-Baptiste Biot, together with compatriot Felix Savart , discovered that the intensity of the magnetic field set up by a current flowing through a wire varies inversely with the distance from the wire. This is now known as Biot-Savart's Law and is fundamental to modern electromagnetic theory. They considered magnetism to be a fundamental property rather than taking Ampére's approach which treated magnetism as derived from electric circuits.

1820 Johann Salomo Christoph Schweigger professor of mathematics, chemist and classics scholar at the University of Halle, Germany built the first instrument for measuring the strength and direction of electric current. He named it the "Galvanometer" in honour of Luigi Galvani rather than a "Schweiggermeter"???. Galvani was in fact unaware of the concepts of current flows and magnetic fields.

1820 Dominique François Jean Arago in France demonstrated the first electromagnet, using an electric current to magnetise an iron rod.

1820 American chemist Robert Hare developed high current galvanic batteries by using spiral wound electrodes to increase the surface area of the plates in order to achieve the high current levels used in his combustion experiments. He also used such batteries in 1831 to enable blasting under water.

Hare also developed an apparatus he called the Spiritoscope, designed to detect fraud by Spiritualist mediums, and in the process of testing his machine, he became a Spiritualist convert and eventually became one of the best known Spiritualists in the USA.

1821 Prussian physicist Thomas Johann Seebeck discovered accidentally that a voltage existed between the two ends of a metal bar when one end was cooled and the other heated. This is a thermoelectric effect in which the potential difference depends on the existence of junctions between dissimilar metals (in this case, the bar and the connecting wire used to detect the voltage). Now called the Seebeck effect, it is the basis of the direct conversion of heat into electricity and the thermocouple. See also the Peltier effect discovered 13 years later which is the reverse of the Seebeck effect.

Batteries based on the Seebeck effect were introduced by Clamond in 1874 and NASA in 1961.

1821 The English scientist Michael Faraday was the first to conceive the idea of a magnetic field which he demonstrated with the distribution pattern of iron filings showing lines of force around a magnet. Prior to that, electrical and magnetic forces of attraction and repulsion had been thought to be due to some form of action at a distance.

In 1821 Faraday made the first electric motor. It was a simple model that demonstrated the principles involved. See diagram. Current was passed through a wire that was suspended into a bath of mercury in the centre of which was a vertical bar magnet. The mercury completed the circuit between the battery and the wire. The current interacting with the magnetic field of the magnet caused the wire to rotate in a circular path around the magnetic pole of the magnet. This was the first time that electrical energy had been transformed into kinetic energy. In 1837 Davenport made the first practical motor but it did not achieve commercial success and for forty years after Faraday's original invention the motor remained a laboratory curiosity with many wierd and wonderful designs. Typical examples are those of Barlow (1922) and Jedlik (1928).

This invention was the source of a bitter controversy with Humphry Davy and William Hyde Wollaston who had tried unsuccessfully to make an electric motor. Faraday was unjustly accused of using Wollaston's ideas without acknowledging his contribution. The upshot was that Faraday withdrew from working on electromagnetics for ten years concentrating instead on chemical research.

Consequently it was not until 1831 that Faraday invented a generator or dynamo to drive the motor. Surprisingly nobody else in the intervening ten years thought of it either. Faraday had shown that passing a current through a conductor in a magnetic field would cause the conductor to move through the field but nobody at the time thought of reversing the process and moving the conductor through the field (or conversely moving a magnet through a coil) to create (induce) a current in the conductor.

In an ideal electrical machine, the energy conversion from electrical to mechanical is reversible. Applying a voltage to the terminals of a motor causes the shaft to rotate. Conversely rotating the shaft causes a voltage to appear at the terminals, thus acting as a generator. It was not until 1867 that the idea of a reversible machine occurred to Werner Siemens and practical motor-generators were not realised until 1873 by Gramme and Fontaine.

Faraday, the Father of Electrical Engineering, was a humble man with no formal education who started his career as an apprentice bookbinder. Inspired by the texts in the books with which he worked and with tickets given to him by a satisfied customer, he attended lectures in 1812 given by the renowned chemist, Sir Humphry Davy, at the Royal Institution. At each lecture Faraday took copious amounts of notes, which he later wrote up, bound and presented to Davy. As a consequence Faraday was taken on by Davy as an assistant for lower pay than he received in his bookbinding job. During his years with Davy he carried out much original work in chemical research including the isolation new hydrocarbons but despite his achievements he was treated as a servant by Davy's wife and by Davy who became increasingly jealous of Faraday's success. Davy also opposed Faraday's 1824 application for fellow of Royal Society when he himself was president. Davy died prematurely in 1829 it is said from inhaling many of the gases he discovered or investigated.

Faraday went on to eclipse his mentor discovering electrical induction, inventing the electric motor, the transformer, the generator and the variable capacitor and making major contributions in the fields of chemistry and the theoretical basis of electrical machines, electrochemistry , magneto-optics and capacitors. His inventions and theories provided the foundations of the modern electrical industry but Faraday never commercialised any of his ideas concentrating more on teaching. He was perhaps the greatest experimenter of his time and although he lacked mathematical skills, he more than made up for it with his profound intuition and understanding of the underlying scientific principles involved which he was able to convey to others. He used his public lectures to explain and popularise science, a tradition still carried on in his name by the IEE today.

Although he was noted for his many inventions, Faraday never applied for a patent.

In 1864 he was offered the presidency of the Royal Institution which he declined. Not so well known is his relationship with Ada Lovelace who idolised him and pursued him over a period of several months in 1844 writing flattering and suggestive letters to which he replied, however in the end he did not succumb to her charms.

When the British Prime Minister asked of Faraday about a new discovery, "What good is it?", Faraday replied, "What good is a new-born baby?"

Saint Michael? - Among Victorian scientists and experimenters, Faraday is revered for his high moral and ethical standards. A deeply religious man, he overcame adversity to become one of the nineteenth century's greatest scientists and an inspiring teacher commanding admiration and respect, but he was not entirely beyond criticism. In 1844 a massive explosion in the coal mine of the small Durham mining village of Haswell killed 95 men and boys, some as young as 10 years old: - most of the male population of the village. The mine owners would accept no responsibility for the disaster and the coroner refused to allow any independent assessor to enter the mine. Incensed, the local villagers took their grievance all the way to the Prime Minister, Sir Robert Peel. Such was the national concern that Peel dispatched two eminent scientists to investigate, Faraday the "government chemist" and Sir Charles Lyell the "government geologist". Their verdict was "Accidental death" and, pressurised by the coroner, they added "No blame should be attached to anyone". In the days before social security, the consequences of this verdict were destitution for the bereaved families.

Faraday's biographers who mention the Haswell mining disaster usually only recount the story that Faraday conducted the proceedings while seated on a sack which, unknown to him, was filled with gunpowder.

1822 English mathematician Peter Barlow built an electric motor driven by continuous current. It used a solid toothed disc mounted between the poles of a magnet with the teeth dipping into a mercury bath, similar in principle to the Faraday disk. Applying a voltage between the shaft and the mercury caused the disc to rotate, the contact with the moving teeth was provided by the mercury.

1823 Johann Wolfgang Döbereiner discovered that hydrogen gas "spontaneously" ignited in the oxygen of the air when it passes over finely spread metallic platinum. He used the phenomenon, an example of what we now call catalysis although he was not aware of it, in the design of a "Platinum Firelighter".

1824 Pure Silicon first isolated by Berzelius who thought it to be a metal while Davy thought it to be an insulator.

1824 While steam engines were still in their infancy, twenty eight year old French physicist and military engineer, Nicolas Léonard Sadi Carnot published "Réflexions sur la Puissance Motrice du Feu" ("Reflections on the Motive Power of Fire") in which he developed the concept of an idealised heat engine: the first theoretical treatment of heat engines. He pointed out that the efficiency of a heat engine depends on the temperature difference of the working fluid before and after the energy conversion process. This was later stated as:

where η is the maximum efficiency which can be achieved by the energy conversion, T_h is the input (hot) temperature of the working fluid in degrees Kelvin and T_c is its output (cold) temperature. This became known as Carnot's Efficiency Law and still holds good today for modern steam turbines and geothermal energy conversion. Carnot also showed that in a reversible process some energy would always be lost providing an early insight into the Second Law of Thermodynamics.

1825 Ampère quantified the relationship between electric current and the changing magnetic field that produces it, now known as Ampère's Law, and laid the foundation of electromagnetic theory. Ten years later Gauss derived an equivalent equation for electric fields.

1825 British electrician, William Sturgeon credited with inventing the first practical electromagnet (5 years after Arago), a coil, powered by a single cell battery, wrapped around a horseshoe magnet. The world's first controllable electric device.

1825 To view electrical discoveries in the context of other key events in the Industrial Revolution, it was in this year that the Stockton and Darlington Railway, the world's first public railway was opened with George Stephenson at the controls of his steam engine the Locomotion pulling 36 wagons - twelve carrying coal and flour, six for guests and fourteen wagons full of workmen. Five years later in 1930 Stephenson's Rocket was successful at the Rainhill trials and was adopted as the engine for the new Liverpool Manchester railway starting a frenzy of railway building - revolutionising the transport of goods, changing the patterns of industrial development, bringing travel within the possibility of the masses and with it - new aspirations.

1826 Italian physicist Leopoldo Nobili together with fellow Italian Macedonio Melloni developed a thermoelectric battery based on the Seebeck effect, constructed from a bank of thermocouples each of which provided a very low voltage of about 50 milliVolts. Nobili also invented a very sensitive astatic galvanometer which compensated for the effect of the earth's magnetic field. The pointer was a compass needle suspended on a torsion wire in the current carrying coil. A second compass needle outside of the coil compensated for any external fields.

1826 German physicist and chemist Johann Christian Poggendorff invented the mirror galvanometer for detecting an electric current.

1827 German physicist Georg Simon Ohm discovered the relationship between voltage and current, V=IR, in a conductor which is now called Ohm's Law. The importance of this relationship lies less in the simple proportionality but on Ohm's recognition that Voltage was the driver of current.

1827 Scottish botanist Robert Brown studying the suspension of pollen in water, observed the random movement of the grains we now call Brownian Motion. These random movements which were later quantified using statistical methods are also typical of the movement of electrons and ions in an electrolyte. This causes of this phenomenon were eventually explained in 1905 by Albert Einstein using the kinetic theory of gases.

1828 Berzelius compiled a table of relative atomic weights for all known elements and developed the system of symbols and formulas for describing chemical actions.

1828 Self taught English mathematician George Green, who worked in his family's windmill till the age of forty, published in a local journal in Nottingham with only 51 subscribers, mostly family and friends, An Essay on the Application of Mathematical Analysis to the Theories of Electricity and Magnetism. It earned him a place at Cambridge as a mature student but its full importance was not recognised at the time until it was rediscovered by William Thomson (later Lord Kelvin) just after his graduation in 1845. Kelvin recognised this as a seminal influence in the development of electromagnetic theory.

1828 French physiologist and biologist René Joachim Henri Dutrochet discovers osmosis - the diffusion of a solvent through a semi permeable membrane from a region of low solute concentration to a region of high solute concentration. The semi permeable membrane is permeable to the solvent, but not to the solute, resulting in a chemical potential difference across the membrane which drives the diffusion. Thus the solvent flows from the side of the membrane where the solution is weakest to the side where it is strongest, until the solution on both sides of the membrane is the same strength equalising the chemical potential on both sides of the membrane.

Semi permeable membranes are now widely used as separators in batteries and fuel cells allowing the passage of certain ions while blocking others.

1828 Hungarian priest and physicist of Slovak origin, Ányos Jedlik built the first direct current electric motor using an electromagnet for the rotor and a commutator to achieve unidirectional rotation. Jedlik's motor was a shunt wound machine in which a moving electromagnet rotated within a fixed coil, the reverse of modern conventional motors. The wires powering the electromagnet protruded into two small semicircular mercury cups on either side of the shaft. This provided the required commutation as the wires picked up the current from alternate cups as the shaft rotated. Like many motors at the time, it had no practical application, however in 1855 Jedlik built another motor based on similar principles which was capable of carrying out useful work.

In 1861 he demonstrated a self excited dynamo but he did not publish his work. Subsequently Siemens, Varley and Wheatstone were credited with the invention.

Jedlik continued working on high voltage generators and spent his last years in complete seclusion at the priory in Gyór.

1829 Nobili invents the thermopile, an electrical instrument for measuring radiant heat and infra red radiation. It was also based on the Seebeck effect as in Nobili's thermoelectric battery of three years earlier and consisted of a sensor made up from a bank of thermocouples connected in series which generated an electrical current in response to the heat radiation input. The current was measured by an astatic galvanometer, of Nobili's own design. With improvements from Melloni, it found extensive use in nineteenth century laboratories.

1829 French physicist Antoine-César Becquerel, father of a dynasty of famous scientists, developed the Constant Current Cell. The forerunner of the Daniell cell, it was the first non-polarising battery, maintaining a constant current for over an hour unaffected by polarisation. It was a two electrolyte system with copper and zinc electrodes immersed in copper nitrate and zinc nitrate electrolytes respectively, separated by a semi permeable membrane. It was left to Daniell to explain how it worked and thus to get credit for the idea.

1830 The thermostat made from a bi-metallic strip, usually brass and copper, invented by Andrew Ure a Glasgow chemistry professor. It did not find much use for 70 years until the advent of electricity supplies to the home when it could be used to operate a switch.

1830 Joseph Henry in the USA worked to improve electromagnets and was the first to superimpose coils of wire wrapped on an iron core. It is said that he insulated the wire for one of his magnets using a silk dress belonging to his wife. An early example of insulated wire. In 1830 he observed electromagnetic (mutual) induction between two coils and his demonstration of self-induction predates Faraday, but like much of his work, he did not publish it at the time. An unfortunate tendency which he lived to regret. (See 1835 Morse)

1831 Faraday invented the solenoid and independently discovered the principle of Induction and demonstrated it in an induction coil or transformer. The induction coil has since been "invented" by many others (See 1886 William Stanley). Faraday was the first to generate electricity from a magnetic field by pushing a magnet into a coil. He put this to practical use with his invention of the generator or dynamo, unshackling the generation of electricity from the battery. Faraday's dynamo, named the Faraday Disk after its construction, consisted of a copper disk rotating between the poles of a magnet. Current is generated along the radius of the disk where it cuts the magnetic field and is extracted via brushes contacting the shaft and the edge of the disk. See diagram. The Faraday Disk functions equally well as a motor and although the machine is said to be unique in that it is a direct current machine which does not need a commutator, it does owe something to Barlow's 1922 toothed motor design. (See also Siemens 1867).

From his experiments Faraday defined the relationship now known as Faraday's Law of Induction which states that the magnitude of the emf induced in a circuit is proportional to the rate of change of the magnetic flux that cuts across the circuit. It was left to Maxwell to express Faraday's Law and his notions of Lines of Force in mathematical terms.

1831 Henry demonstrated a simple telegraph system sending a current through a mile and a half of wire to trigger an electromagnet which struck a bell (thereby inventing the electric bell, for many years the main domestic use of the battery). He used a simple coding system switching the current on and off to send messages down the line. Henry thought that patents were an impediment to progress and like Faraday he believed that new ideas should be shared for the benefit of the community. He subsequently freely shared his ideas on telegraphy with S. F. B. Morse who however went on to patent them passing them off as his own.

1831 -1835 Henry developed the relay which was used as an amplifier rather than as a switch as it is used today. At the end of each section, the feeble current would operate a relay which switched a local battery on to the next section of the line renewing the signal level. This enabled signals (currents) to be carried (relayed) over long distances making possible long distance telegraphy. In fact the relay reconstituted the signal rather than amplified it, just as the repeaters used in modern digital circuits do, thus avoiding amplifying the noise. The relay and its use with local battery power to "lengthen the telegraph line" were more of Henry's ideas which he failed to publicise or exploit.

For over thirty years telegraphy was the main practical application of the battery, this new found electrical technology.

1832 After witnessing a demonstration of von Sömmering's electrochemical telegraph some time earlier, Baron Schilling an attaché at the Russian embassy in Munich, in turn developed the idea by making an electromagnetic device which he demonstrated in 1832. It was a six wire system which used the movement of five magnetic needles to indicate the transmission of a signal. This was the method subsequently used by Cooke and Wheatstone who later "invented" and patented the five needle electric telegraph for two way communications in 1837.

1832 Hippolyte Pixii built his "magneto generator" the first practical application of Faraday's dynamo. The term "magneto" means that the magnetic force is supplied by a permanent magnet. His first machine rotated a permanent magnet in the field of an electromagnet generating an alternating current for which there was no practical use at the time. The following year at Ampère's suggestion he added a commutator to reverse the direction of the current with each half revolution enabling unidirectional - direct current to be produced. Pixii's magneto liberated electrical experimenters from their dependence on batteries.

1833 Faraday published his quantitative Laws of Electrolysis which express the magnitudes of electrolytic effects and galvanic reactions, putting Volta's discoveries and battery theory on a firm scientific basis.

With William Whewell, he also coined the words, electrode, electrolyte, anode (Greek - Way in), cathode (Greek - Way out) and ion (Greek - I go) .

1833 Samuel Hunter Christie of the British Royal Military Academy publishes a bridge circuit for comparing or determining resistance, later to be called the Wheatstone Bridge.

1833 German physicist Wilhelm Eduard Weber, working with Gauss, demonstrated "the world's first electric telegraph" operating over a distance of 3 kilometers. One of many such claims before and since. The system used a simple coding scheme switching the current on and off, similar to Henry's, combined with reversing the polarity of the current to deflect a compass needle in opposite directions, to send different letters down a single wire. Over the subsequent years Weber investigated terrestrial and induced magnetic fields and verified the theoretical laws put forward by Ampère and others using electrical instruments which he designed for this purpose. The unit of Magnetic Flux is named the Weber in his honour.

1833 Russian physicist Heinrich Friedrich Emil Lenz formulated Lenz Law which states that an induced electric current flows in a direction such that the current opposes the change that induced it. A special case of the Law of Conservation of Energy. The law explains that when a conductor is pushed into a strong magnetic field, it will be repelled and that when a conductor is pulled out of a strong magnetic field that the magnetic forces created by the induced currents will oppose the pull. This also explains the phenomenon of back emf in electric motors, that is, the voltage created by the moving armature which opposes the applied voltage and hence the movement of the armature itself. Lenz law was later extended for more general application by Le Chatelier.

In the same year he also showed that the resistance of a metal increases with temperature.

1833 Scottish chemist Thomas Graham discovers the rate at which a gas diffuses is inversely proportional to the square root of the density of the gas. Now known as Graham's Law of Diffusion. Diffusion however is not confined to gases, it can take place with matter in any state. It may take place through a semi permeable membrane, which allows some, but not all, substances to pass. In solutions, when the liquid solvent passes through the membrane but the solute (dissolved solid) is retained, the diffusion process is called osmosis, a process which is used in many battery designs.

1834 French clockmaker Jean Charles Athanase Peltier discovered that when a current flows through a closed loop made up from two dissimilar metals, heat is transferred from one junction between the metals to the other and one junction heats up while the other cools down. Used as the basis for refrigeration products with no moving parts. This is now known as the Peltier effect and is the reverse of the Seebeck effect discovered 13 years earlier.

1835 German mathematician Carl Friedrich Gauss quantified the relationship between the electric flux flowing out a closed surface and the charge enclosed in the surface. Now know as Gauss's Law it is the electrical field equivalent of Ampère's Law for magnetic fields. It was not published however until 1867.

Gauss also did pioneering work on probability and statistics, defining and characterising the Normal Distribution, now also named the Gaussian Distribution in his honour. It is the theoretical basis of much of today's quality control of which Six Sigma is an example.

Gauss was one of the worlds most gifted and prodigious mathematicians making major contributions to geometry, algebra, statistics, probability theory, differential equations, electromagnetics, and astronomy. Working alone for much of his life Gauss' personal life was, like Ampère's, tragic and complicated. His first wife died early, followed by the death of one of his sons, plunging him into a depression which was not helped by an unhappy second marriage which also ended with the early death of his second wife.

While he was working, when informed that his wife is dying Gauss replied: "Ask her to wait a moment - I am almost done. "

1835 Samuel Finley Breese Morse, American artist and professor of the Literature of the Arts of Design in the University of the city of New York and religious bigot with a mandate directly from God, made a career change at the late age of 41and started work on telegraphy. Undaunted by his lack of knowledge of the principles of electricity, he sought the assistance in developing his ideas, first from a colleague Leonard Gale of the University of New York who pointed out to Morse the need for insulation on the windings of his electromagnets, and then from Joseph Henry who already had a working telegraph system and who explained the need for relays to extend the range of the system. Morse subsequently patented Henry's ideas in his own name. He demonstrated the "first" electric telegraph in 1835 ignoring many prior claims dating as far back as Gray in 1729, Morrison's design of 1753 and Salvá's in 1804 as well as more practical recent inventions by Henry in 1831 and Weber in 1833.

Morse patented his system in 1837 and although it came after the needle telegraphs of Schilling (1832) and that of Cooke and Wheatstone (1837) which was patented earlier the same year as Morse's, Morse's system was simpler and more robust using only a single signalling wire plus a return wire and its use spread very quickly.

Morse subsequently claimed sole authorship for these ideas and also for the relay, another of Henry's inventions ignoring Henry's essential contributions to the system thus creating an irreparable rift with Henry. Similarly, the coding system Morse Code on which single channel telegraphy depends was based on existing technology including Henry's ideas, as well as those of Gauss and Weber, which Morse developed jointly with Albert Vail, Morse's business partner. It was Vail who invented the Morse key and also the printing telegraph which was patented in Morse's name. Their relative contributions are still in dispute. (See also 1841 Bain)

Henry is reported to have said in later life "If I could live my life again, I might have taken out more patents".

For 35 years the battery was a solution looking for a problem. It had been used on a small scale as a laboratory tool providing the energy for electrolysis in the analysis of chemical compounds and the isolation of new elements but it was Morse's electric telegraph which eventually created the deployment of batteries on an industrial scale.

1835 Electric arc welding proposed by James Bowman Lindsay of Dundee. The idea was eventually patented fifty years later by Benardos and Olszewski in 1885.

Lindsay had many bright ideas, including the design for an electric light which he demonstrated in 1836 and several innovations in the field of telegraphy but none of these were ever commercialised.

1836 Demonstration by a British chemist John Frederic Daniell of the Daniell cell, a two electrolyte system using two electrodes immersed in two fluid electrolytes separated by a porous pot.

Volta's simple voltaic cell cannot operate very long because bubbles of hydrogen gas collect at the copper electrode acting as an insulator, reducing or stopping further electron flow. This blockage is called polarisation. Daniell's cell overcomes this problem by using electrolytes which are compatible with the electrodes. Thus the zinc electrode is suspended in an electrolytic solution of zinc sulphate which is contained in the porous pot (Initial designs used sulphuric acid rather than zinc sulphate). The porous pot is in turn immersed in the copper sulphate solution which is contained in a glass jar into which the copper electrode is also suspended. The Daniell cell does not produce gaseous products as a result of galvanic action and copper rather than hydrogen is deposited on the cathode. Daniell's non-polarising battery was thus able to deliver sustained, constant currents, a major improvement on the Voltaic pile.

The Daniell cell chemistry was also available in other configurations which provide superior performance such as the gravity cell or crowfoot cell which eliminated the porous pot.

Daniell's cell was however based on a similar non polarising battery design demonstrated by Becquerel in 1829 which used nitrate electrolytes rather than the sulphate electrolytes used by Daniell. Despite the prior art, Daniell, rather than Becquerel, is remembered as the inventor of the non-polarising cell.

Early galvanic cells were all based on acidic electrolytes and many of these designs produced hydrogen at the cathode causing the cell to become polarised. Two approaches were adopted to solve the polarisation problem. Daniell's solution was a non-polarising cell which did not produce hydrogen. The other alternatives were depolarising cells containing oxidising compounds which absorbed the hydrogen as it was produced and did not allow the build up of bubbles. The Leclanché cell which uses manganese dioxide as a depolariser is an example of this type.

1836 Although it had been known for many years that some chemical processes could be speeded up by the presence of some unrelated chemical agent which was not consumed by the chemical action and that the phenomenon had been used by Döbereiner and others, it was Berzelius who in 1836 introduced the term catalyst and elaborated on the importance of catalysis in chemical reactions.

1836 Parisian craftsman Ignace Dubus-Bonnel was granted a patent for the spinning and weaving of glass. His application was supported by a small square of woven fibreglass. The drawn glass was kept malleable by operating in a hot vapour bath and weaving was carried out in a room heated to over 30°C.

1836 Irish priest, scientist, and inventor, Nicholas Joseph Callan, working at Maynooth Theological University in Ireland, invented of the induction coil. He discovered that by interrupting a low current through a small number of turns of thick copper wire making up the primary winding of an induction coil, a very high voltage could be induced across the terminals of a high turns secondary winding of thinner copper wire on the same iron core. Such induction coils are used in the automotive industry to operate the sparking plugs, but in the other industries they are generally known as Ruhmkorff coils.

The importance of Callan's pioneering work was not recognised at his remote institution which had other priorities and he never received recognition for this invention which is now associated with the name of German-born Parisian instrument maker, Heinrich Ruhmkorff. Like all instrument makers, he put his name on every instrument he made and Callan's coil eventually become known as the "Ruhmkorff Coil".

1837 Faraday discovers the concept of dielectric constant, invents the variable capacitor and states the law for calculating the capacitance. The unit of Capacitance the Farad is named in his honour.

1837 Sixteen years after the principle was demonstrated by Faraday, self taught American blacksmith Thomas Davenport patented the first practical electric motor as "an application of magnetism and electro-magnetism to propelling machinery." Powered by a galvanic battery consisting of a bucket of weak acid containing concentric cylindrical electrodes of dissimilar metals, the motor was a shunt wound, brush commutator device. The magnetic field of the stator was provided by two electromagnets. Two further electromagnets formed the spokes of a wheel which acted as the rotor. The commutator reversed the polarity of the rotor electromagnets as they passed the alternate north and south poles of the stator to create unidirectional rotation. It was granted the first ever patent for an electrical machine.

Davenport's "revolutionary" invention was ahead of its time and it did not bring him the commercial success his efforts deserved. At the time, the lack of suitable batteries or any other source of electrical power to drive the motor inhibited its adoption and his persevering endeavours to improve and promote the motor led him into bankruptcy. His pioneering use of electromagnets in both the stator and the rotor of his machine went largely unnoticed until the idea was reinvented simultaneously by Varley, Siemens and Wheatstone in 1866 for use in their designs for dynamos. It was not until forty years after Davenport's invention that the demand for electric motors eventually took off. Unfortunately Davenport didn't live to see it. He died aged 49 in 1851.

1837 Patent granted for a Needle electric telegraph (Two way electric communications) conceived by William Fothergill Cooke, a retired English surgeon of the Madras army studying anatomy at the University of Heidelberg, and refined by physicist Sir Charles Wheatstone of King's College, London. (See 1816 Ronalds) This was claimed to be the first practical battery powered telegraph, however it is very similar to Schilling's design of 1832. An elegant design, instead of using one wire for each letter it used only five signalling wires plus a return wire. By using a combination of the five signalling needles the number of wires could be reduced. When activated, the needles pointed to individual letters on a board. Twenty different letters could be identified by only five wires. There was no provision for sending the letters C, J, Q, U, X and Z. The design was overtaken by the simpler single wire system devised Morse using his coding system of dots and dashes. The relationship between Cooke and Wheatstone eventually ended acrimoniously over a dispute about their respective contributions to the design.

1837 First commercially available insulated wire made by British haberdasher W. Ettrick who adapted silk wound "millinery" wire, used in hat making, for electrical purposes. The same year William Thomas Henley made a six head wire wrapping machine for manufacturing silk insulated wire and founded Henley Cables.

1837 James W. McGauley of Dublin invented the self acting circuit breaker in which the electric current moved an armature which opened the circuit switching off the current. When the current was removed the armature moved back to its original position and switched on the current once more causing the armature to oscillate and the current to be switched rapidly on and off. The same year American inventor Charles Grafton Page built a similar device which he called a rocking magnetic interrupter. The original purpose of these devices was to provide current pulses to the primary of an induction coil causing repetitive high voltage sparks at the terminals of the secondary winding. This trembler mechanism was subsequently widely used in electric bells, buzzers and vibrators.

1838 Scottish engineer Robert Davidson built a DC electric motor based on iron rotor elements driven by pulses from electromagnets in the stator. It was the first example of what we would now call a switched reluctance motor. The motor comprised two electromagnets one on either side of a wooden rotor and three axial iron bars equally spaced around the periphery of the rotor. The electromagnets were switched on and off in turn by means of a mechanical commutator driven from the rotors.

Davidson used four of these motors to drive a 5 ton electric locomotive on the newly opened Edinburgh/Glasgow railway in 1842 reaching a speed of 4 mph over a distance of one and a half miles.

The vehicle was powered by two large batteries constructed from wooden troughs each with 20 cells containing sulphuric acid in which were suspended zinc and iron electrodes. The motor speed was controlled by lowering or raising the electrodes into and out of the acid. A resin sealant protected the wooden cells from attack by the acid.

Like Davenport's motor, Davidson's motor was also ahead of its time and was not developed into a practical product. The more efficient electromagnetic rotors and stators as pioneered by Davenport, became the norm and the reluctance motor was forgotten. It was however revived in the 1960's when new semiconductor technology made electronic commutation possible and, because of its simplicity, the reluctance motor finds many uses today.

1838 Carl August von Steinheil a German physicist discovers the possibility of using the "earth return" or "ground return" in place of the current return wire for the signal in telegraph circuits thus enabling communications using a single wire.

1839 Welsh lawyer Sir William Robert Grove demonstrates the first Fuel Cell. Attempting to reverse the process of electrolysis by combining hydrogen and oxygen to produce water, he immersed two platinum strips surrounded by closed tubes containing hydrogen and oxygen in an acidic electrolyte. His original fuel cell used dilute sulfuric acid because the reaction depends upon the pH when using an aqueous electrolyte. This first fuel cell became the prototype for the Phosphoric Acid Fuel Cell (PAFC) which has had a longer development period than the other fuel cell technologies.

The same year Grove also demonstrated an improved two electrolyte non-polarising galvanic cell using zinc and sulphuric acid for the anodic reaction and platinum in nitric acid for the cathode. Known as the Grove cell it provided nearly double the voltage of the first Daniell cell. Grove actually developed a rechargeable cell however there were few facilities for recharging at that time and the honour for inventing the secondary cell eventually went to Planté in 1860. Grove's nitric acid cell was the favourite battery of the early American telegraph systems (1840-1860), because it offered high current output. However it was found that the Grove cell discharged poisonous nitric dioxide gas and large telegraph offices were filled with gas from rows of hissing Grove batteries. Consequently, by the time of the American Civil War, Grove's battery was replaced by the Daniell battery.

1839 Prussian engineer Moritz Hermann von Jacobi financed by Czar Nicholas makes first electric powered boat using 128 Grove cells. He also formulated the law known as the Maximum Power Theorem or Jacobi's Law which states: "Maximum power is transferred when the internal resistance of the source equals the resistance of the load". Also known as Load matching.

In 1838 von Jacobi also discovered electroforming by which duplicates could be made by electroplating metal onto a mould of an object, then removing the mould. This galvanic process was used for making duplicate plates for relief or letterpress printing when it was called electrotyping.

1839 Alexandre-Edmund Becquerel discovered the photovoltaic effect when he was only nineteen while experimenting with an electrolytic cell made up of two metal electrodes placed in an electrically conducting solution. He noticed that small currents were generated between the metals on exposure to light and these currents increased with the light intensity. This new source of electricity never had the same impact as the Volta's cells since the currents were small and the phenomenon was largely ignored by the scientific community. 100 years later Becquerel's discovery was recognised as the first known example of a P-N junction. See also Becquerel 1896

1839 Polystyrene isolated from natural resin by German apothecary Eduard Simon however he was not aware of the significance of his discovery which he called Styrol. Its significance as a plastic polymer with a long chain of styrene molecules was recognised by Staudinger in 1922.

1840 James Prescott Joule an English brewer published "On the Production of Heat by Voltaic Electricity" showing that the heat produced by an electric current is proportional to I²R now known as Joule's Law. He also discovered that electrical power generated is proportional to the product of the current and the battery voltage and he established that the various forms of energy, mechanical, electrical, and heat - are basically the same and can be changed, one into another. Thus he formed the basis of the law of Conservation of Energy, now called the First Law of Thermodynamics.

1840 Robert Sterling Newall from Dundee patented a wire rope making machine suitable for manufacturing undersea telegraph cables. It was used to make the first successful telegraph cable connecting England and France in 1851 and later with others the first transatlantic telegraph cable. The cable was insulated with gutta-percha, the adhesive resin of the isonandra gutta tree, introduced to Europe in 1842 by Dr. William Montgomerie, a fellow Scot working as a surveyor in the service of the East India Company. Gutta percha was used for 100 years for cable insulation until it was eventually replaced by polyethylene (commonly called polythene) and PVC.

1840 Electroplating, a process discovered by Cruikshank forty years earlier, was re-invented by the Elkingtons of Birmingham and commercialised by Thomas Prime. Articles to be plated were suspended as one electrode in a bath containing an electrolyte of silver or gold dissolved in cyanide. When the voltage was applied to the electrodes the metal was deposited on the suspended article.

1840 Eminent British mathematician and Astronomer Royal, George Biddell Airy, develops a feedback device for continuously manoeuvering a telescope to compensate for the earth's rotation. Problems with his mechanism led to Airy becoming the first person to discuss instability (hunting or runaway) in closed-loop control systems and the first to analyse them using differential equations. Stability criteria were later established by Maxwell.

Feedback control systems were not new. The list below gives some examples from earlier times:

Considering his track record, Airy surprisingly held the post of Astronomer Royal, the highest office in the British civil service, for forty six years. Filled with his own self importance he belittled the work of those whom he considered his social inferiors such as Faraday whose mathematics, in his view, wasn't up to scratch and John Couch Adams who predicted the existence and orbit of the planet Neptune and whom Airy ordered to proceed slowly and re-do his calculations "in a leisurely an dignified manner". Consequently Airy missed its eventual discovery which was scooped by Frenchman Urbain Jean Joseph Le Verrier.

In his role as chief scientific advisor to the government he put a premature end to Babbage's pioneering work on computers with his verdict, "I believe the machine to be useless, and the sooner it is abandoned, the better it will be for all parties", which cut off all government funding for the project.

Airy also advised against the construction of the Crystal Palace to house the Great Exhibition of 1851 because he said the structure would collapse when the salute guns were fired. Despite Airy's objections, it was built anyway and was a great success.

After the Tay Bridge disaster in 1879 when the bridge collapsed into the river during a storm killing all 75 passengers on the train passing over it at the time, the subsequent investigation found that Airy, who who provided the wind loading for designer Thomas Bouch, seriously miscalculated the effect of a Tayside gale on the structure, and that the bridge would have fallen "even if construction had been perfect".

1840 "Steam Electricity" , electrostatic discharges produced by the frictional electrification of water droplets, observed by a colliery "Engine Man" near Newcastle in England when probing a steam leak. The phenomenon was investigated by local lawyer, (later to be engineer and arms manufacturer), William George Armstrong who constructed what he called a Hydro-Electric Generator using the effect to produce electrostatic charges on demand. It consisted of a boiler insulated from the ground generating a jet of steam from which sparks could be drawn on to an insulated metallic conductor. The conductor became positively charged, while the boiler acquired a negative charge.

1841 The non-polarisng Carbon-Zinc cell, substituting the cheaper carbon for the expensive platinum used in Grove's cell, invented by German chemist Robert Wilhelm Bunsen. His battery found large scale use for powering arc-light and in electroplating.

Bunsen did not invent the eponymous burner for which he is famous. The basic burner was in fact invented by Faraday and improved by Peter Desaga, a technician working for Bunsen at the University of Heidelburg. The improved burner was designed to provide the high temperature flames needed for Bunsen's joint studies of spectroscopy with Kirchhoff and Desaga was smart enough to manufacture and sell the new device under his boss's name.

Bunsen never married. He was a popular teacher who delighted in working with foul smelling chemicals. Early in his career he lost the use of his right eye when an arsenic compound, cacodyl cyanide, with which he was working, exploded.

1841 Scottish clockmaker Alexander Bain invented the first pendulum electric clock. Bain demonstrated his clock to Charles Wheatstone who copied the clock and three months later demonstrated it to the Royal Society claiming it as his own invention. Fortunately, unknown to Wheatstone, Bain had already patented the invention.

Bain also proposed a method of generating electricity to power his clock by means of an earth battery. This consisted of two square plates of zinc and copper, about two feet square, buried deep in the ground a short distance apart forming a battery with the earth acting as the electrolyte. Such an arrangement produces about one volt continuously.

1843 Alexander Bain patented a device to scan a two-dimensional surface and send it over wires. Thus, the patent for the fax machine and the first use of scanning to dissect and build up an image was granted 33 years before the patent was given for the telephone. Over a period of five years Bain designed and patented many improvements to the electric telegraph including the use of punched tape (re-invented by Wheatstone and sold to Samuel Morse in 1857) which were widely adopted at the time. Unfortunately he derived no financial benefit from his ideas. His efforts and his money were spent in pursuing patent infringements by Samuel Morse and he retired into a life of obscurity, poverty and hardship.

1843 The first computer program was written by Augusta Ada Byron, Countess of Lovelace to calculate values of a Bernoulli function. Known as Ada Lovelace she was the beautiful daughter of romantic English poet Lord Byron and wife of the Earl of Lovelace. She was tutored by famous mathematician Augustus De Morgan at the University of London and became the world's first software engineer. Convinced of her own genius she let everybody know it at every opportunity. She worked as an assistant to Charles Babbage on the development of his "analytical engine" the world's first programmable computer which used punched cards for input and gears to perform the function of the beads of an abacus.

Before Babbage, computing devices were mostly analogue, performing calculation by means of measurement, Babbage's machine however was digital, performing calculation by means of counting. It is claimed that Ada originated the concept of using binary numbers, a practice used in all modern computers, however Babbage's difference engine and more versatile analytical engine were both based on the decimal numbering system. Her notes indicate that she understood and used the concepts of a stored program, as well as looping, indexing, subroutine libraries and conditional jumps, the first use of logic in a machine, however the extent of Babbage's contribution to these thoughts and how much was her own work is not clear. She wrote "The Analytical Engine ... weaves algebraic patterns, just as the Jacquard-loom weaves flowers and leaves." Though her contribution to the technology may be questioned, her charm did wonders for Babbage's PR (although it didn't quite work on Michael Faraday).

Ada however managed to run up considerable gambling debts with her lover John Crosse and as a solution she applied her mathematical prowess to fresh fields developing a winning "system" for betting on horses (proving, incidentally, that genius and common sense don't always go hand-in-hand). Unfortunately, the horses being unaware of their responsibilities, the system didn't win and Ada finished her life as a bankrupt, alienated from her family, addicted to laudanum (opium), dying a painful death from cancer of the cervix at the age of 36, repeating the demise of her father, also an opium addict who died of a fever at same age of 36.

Babbage did not have the financial resources to complete his machines and he appealed to the Prime Minister Robert Peel for help, but after taking advice from the formidable Astronomer Royal Sir George Airy, the request was turned down and his machines were never finished. In 1991 the British Science Museum completed the construction of Babbage's Difference Engine No.2 from Babbage's original drawings with new components and it worked just as he said it would, performing its first test calculation for the public, the powers of seven (y=x⁷) for the first 100 values.

1843 Sir Charles Wheatstone "found" a description of the Christie's 1833 bridge circuit, now known as the Wheatstone Bridge, and published it via the Royal Society though he never claimed he invented it.

The same year Wheatstone also invented the Rheostat (Greek - "Rheo" Flowing stream) variable resistor.

1843 Patents for the vulcanisation of natural rubber with sulphur to improve its strength, wearing properties and high temperature performance were awarded to Thomas Hancock in England in May 1843 and one month later to Charles Goodyear in the USA. Subsequently patents for hard rubber called vulcanite or ebonite, created by using excess sulphur during vulcanisation, were granted to Hancock in England in 1843 and to Nelson Goodyear (brother of Charles) in the USA in 1851.

Ebonite is a hard, dark and shiny material initially used for jewellery, musical instruments, decorative objects and dental plates (with pink colouring) for nearly 100 years. It is also a good insulator and soon found use in electrical equipment and power distribution panels.

Ebonite was a milestone because it was the first thermosetting material and because it involves modification of a natural material.
Ebonite mouldings were exhibited by both Hancock and Goodyear at the Great Exhibition of 1851.

1843 German founder of modern electrophysiology Emil du Bois-Reymond discovered that nerve impulses were a kind of "electrical impulse wave" which propagated at a fixed and relatively slow speed along the nerve fibre. In 1849, using a galvanometer wired to the skin through saline-soaked blotting paper to minimise the contact resistance, he was able to detect minute electrical discharges created by the contraction of the muscles in his arms. Realizing that the skin acted as an insulator in the signal path, he increased the strength of the signals by inducing a blister on each arm, removing the skin and placing the paper electrodes within the wounds. He determined that a stimulus applied to the electropositive surface of the nerve membrane causes a decrease in electrical potential at that point and that this "point of reduced potential", or impulse, travels along the nerve like a wave.

1845 Michael Faraday discovers that the plane of polarisation of a light beam is rotated by a magnetic field. The first experimental evidence that light and magnetism are related. Now called the Magneto-Optic effect or the Faraday effect.

1845 Gustav Robert Kirchhoff a German physicist at the age of 21 announced the laws which allow calculation of the currents, voltages, and resistances of electrical networks. In further studies, based on Kelvin's mathematical representation of the circuit elements, he demonstrated in 1857 that current flows through a conductor at the speed of light.

Kirchhoff formed a productive working partnership with Bunsen at the University of Heidelburg where they discovered the that the flames of each element had a unique emission and absorption visible light spectrum, founding the science of emission spectroscopy for analysing and identifying chemical substances. They invented the spectroscope which allowed them to analyse not only earthly elements but also to determine the composition of the sun and the stars by spectral analysis of the radiation they emit.

After an accident in early life, Kirchhoff spent most of his working life in a wheelchair or on crutches.

1846 The Smithsonian Institution established in the USA, "for the increase and diffusion of knowledge among men" with a large endowment from English chemist and mineralogist, James Smithson, in neat symmetry with the founding of the Royal Institution in England by the American, Count Rumford. Joseph Henry was chosen as the Smithsonian's first distinguished Secretary. Smithson never visited the United States but after he died his remains were brought there for burial.

1846 From his experiments on magneto optics Faraday discovered that some substances such as heavy glass and Bismuth are repelled rather than attracted by magnets and named the phenomenon diamagnetism. Using the analogy with dielectrics and conductors he made the distinction between diamagnetics - "poor conductors of magnetic force" and paramagnetics - "good conductors of magnetic force".

1848 Scottish physicist, born in Belfast, William Thomson (later Lord Kelvin) established the basis for an absolute temperature scale. Starting from the experimental results of Charles and Gay Lussac, Kelvin showed also that there is an absolute zero of temperature which is -273°C. The absolute temperature scale is named the Kelvin scale in his honour and -273°C is called 0°K or absolute zero.

Kelvin was an infant prodigy in mathematics, entering Glasgow University at the age of ten, he started the undergraduate syllabus when he was only fourteen and published his first scholarly papers, correcting errors in the works of both Fourier and Fourier's critics, when he was only sixteen. Fourier remained an inspiration to him throughout his early years. Kelvin always sought practical analogies to explain his theories and published over 600 scientific papers on mathematics, thermodynamics, electromagnetics, telecommunications, hydrodynamics, oceanography and instrumentation and he filed 70 patents. He is remembered for his work on the Transatlantic Telegraph Cable but he initially gained fame by estimating the age of the earth from a knowledge of its cooling rate at over 100 million years (later revised and broadened from 20 to 400 million years) in contradiction of the prevailing religious, creationist view of the world. Despite this he maintained a strong and simple Christian faith throughout his life and engaged in a long running public disagreement with Charles Darwin, remaining "on the side of the angels", claiming that, according to his calculations, the age of the earth was too short for Darwin's evolutionary changes to have taken place. (Current estimates give the age of the earth as 4.6 billion years taking into account the heating effect of radioactivity of the earth's core, something of which Kelvin could not have been aware). He remained actively involved in scientific work until he was 75 but in later life he found it difficult to accept Maxwell's theories, for which he himself had been the Genesis, and the concept of radioactivity.

According to C Watson, Kelvin's biographer, "During the first half of Thomson's career he seemed incapable of being wrong while during the second half of his career he seemed incapable of being right."

1849 The first accurate terrestrial measurement of the speed of light was made by French physicist Armand Hippolyte Louis Fizeau. Previous measurements had been based on observations of the movement of planets and moons by Danish astronomer Ole Christensen Rømer (1676), English astronomer James Bradley (1728) and others. Fizeau directed a beam of light through the gaps in a rotating cog wheel to a mirror several miles away and observed the reflection of the pulses of light coming back through gaps in the wheel. Depending on the speed of rotation of the wheel, the returning light would either pass though the gap or be blocked by a tooth. The speed of light could be calculated from the distance to the mirror, the number of teeth on the wheel and its rate of rotation. He determined the speed of light to be 186,000 miles per second or 300,000,000 metres per second.

Also known as Einstein's constant, the speed of light is represented by the symbol c for "celeritas" (Latin - "speed").

1849 The Bourdon tube pressure gauge was patented by French engineer Eugene Bourdon. It is still one of the most widely used instruments for measuring the pressure of liquids and gases of all kinds, including steam, water, and air up to pressures of 100,000 pounds per square inch as well as pressures below atmospheric. It consists of a "C" shaped or spiral curved tube sealed at one end which tends to straighten out when a pressurised fluid is admitted into it. The displacement of the end of the tube is used to move a pointer or other indicator.

1850 Prussian born theoretical physicist Rudolf Julius Emmanuel Clausius publishes his seminal paper "On the Mechanical Theory of Heat" establishing the study of Thermodynamics and outlining the basis of the Second Law.

1851 In his treatise "On the Dynamical Theory of Heat." Kelvin formally states the Second Law of Thermodynamics, that "Heat does not spontaneously flow from a colder body to a hotter". It was later restated in the form "In a closed system entropy can only increase", recognising the concept of entropy proposed by Clausius in 1865.

1851 German inventor Heinrich Daniel Ruhmkorff patents the Ruhmkorff Induction Coil capable of producing sparks 30 centimetres long. Basically a high turns ratio transformer, it was invented in 1836 by Irish priest Nicholas Callan.

1852 English chemist Edward Frankland invented the notion of chemical bond and introduced the idea of valency, that an atom of one element could only compound with a definite number of atoms of another element.

1852 Joule and Kelvin (William Thomson) discovered that when a gas is allowed to expand without performing external work, the temperature of the gas falls. Now known as the Joule-Thomson Effect, it is the basis of nearly all modern refrigerators and gas liquefaction processes. (The Peltier Effect is also used in some special cooling applications)

1852 American engineers William F. Channing and Moses Gerrish Farmer installed the first municipal electric fire alarm system using a series of electric bells and call boxes with automatic signaling to indicate the location of a fire in Boston, twenty four years before the advent of the telephone.

Farmer was a prolific inventor in the same mould as Edison. In the same year (1852) he also demonstrated diplex telegraphy, the simultaneous transmission of two signals in the same direction down a wire (or channel), the first example of time division multiplexing (TDM). It was based on two rotating switches, one at each end of the line which connected the transmission line alternately to each transmitter / receiver pair permitting sequential, interleaving of signals from each channel. Unfortunately he was not able to develop it into a practical system because of the difficulty of synchronising the receivers with the transmitters, a problem which was not solved until 1874 by Baudot.

In 1858 he did however patent a two battery duplex system similar to Gintl's 1853 design. (See next). As with the diplexer, there were obstacles to overcome before practical duplexers were ready for roll out. In this case it was the design by Stearns in 1872 which took the honours.

1853 The electric burglar alarm patented by American Minister Augustus Russell Pope. When a door or window was opened, it closed an electrical contact initiating an alarm. The rights to the patent were purchased by Edwin Holmes who began manufacturing and selling the alarms in 1858 and was subsequently credited with its invention.

1853 Austrian telecommunications engineer Julius Wilhelm Gintl working in Vienna, invented a method of duplex telegraphy, the simultaneous transmission of two signals in opposite directions down a wire (or channel). The first telecommunications duplexer - allowing simultaneous message transmission and reception. It was a two battery, "compensating" system with differential relays, in which two samples of the transmitted signal were arranged to cancel eachother in the local receiving relay but were able to operate the remote receiving relay normally.

In 1855 German engineer Carl Frischen working for Siemens & Halske registered of a patent for a simplified version of Gintl's design with only one compensating battery.

1853 Almost 200 years after Newton, Scottish engineer William John Macquorn Rankine introduced the concept of potential energy for stored energy (In mechanical terms - energy based on position). Together with Kelvin they applied the concept to electrical potential whose unit of measurement they named the volt.

1853 Mathematical representation of the voltage-current relationships of capacitors (i = C dv/dt) and inductors (v = L di/dt) derived by Kelvin enabling the analysis of RLC circuits and the performance of telegraph cables. A more detailed model of the cable or transmission line, based on Kelvin's theory, but taking into account the distribution of the capacitance and inductance along the line, was developed by Kirchhoff in 1857.

1854 The fundamental idea of the electrical transmission of sound (the telephone) was published in the magazine "L'Illustration de Paris" by Belgian experimenter Charles Bourseul, working in France.

1854 Heinrich Geissler, a master glassblower in Bonn, Germany, was the first to make use of improved vacuum technology to create a series of astonishingly beautiful evacuated glass vessels into which he sealed metal electrodes. Geissler's vacuum tubes emitted brilliant and colourful fluorescent light when energised by a high voltage which aroused the interest of both scientists and artists of his day.

1854 English mathematician George Boole published "An Investigation of the Laws of Thought, on Which Are Founded the Mathematical Theories of Logic and Probabilities" in which he expressed logical statements in mathematical form. Now known as Boolean Logic it also used a binary approach to represent whether statements were true or false. It made little impact at the time until twelve years latter it was picked up and developed by American logician Charles Sanders Pierce. However it remained in obscurity until it's value was recognised by Claude Shannon in 1937 and used to make improvements to Vannevar Bush's analogue computer the differential analyser. Overnight it became the basic information processing concept used in all modern computers.

Boole's wife, Mary Everest, niece of Sir George Everest after whom the mountain was named, was not blessed with the same logical mind as her husband. in 1864 at the age of 49 Boole caught a serious cold after walking two miles in the rain and giving a lecture still dressed in his wet clothes. His wife believed that a remedy should resemble the cause. She put him to bed and threw buckets of water over the bed since his illness had been caused by getting wet. Boole died of pneumonia.

1855 British chemist and inventor Alexander Parkes produced the first synthetic (man made) plastic. By dissolving cellulose nitrate in alcohol and camphor containing ether, he produced a hard solid which could be molded when heated, which he called Parkesine (later known as celluloid). Unfortunately, Parkes could find no market for the material. In the 1860's, John Wesley Hyatt, an American chemist, rediscovered celluloid and marketed it successfully as a replacement for ivory. Thus was born the plastics industry which brought new opportunities to the electrical industry for both insulation and packaging.

1856 As an extension to his "dynamical theory of heat" published in 1851, Kelvin submitted a paper to the Royal Society outlining the "dynamical theory of electricity and magnetism" treating electricity as a fluid. It was these ideas which led Maxwell to develop his theory of electromagnetic radiation published in 1873.

In the same year Kelvin invented the strain gauge based on his discovery that the resistance of a wire increases with increasing strain.

1857 Following his discovery the previous year that the resistance of a conductor increases with increasing strain Kelvin also discovered that the resistance also changes when the conductor is subjected to an external magnetic field, a phenomenon known as magnetoresistance. In bulk ferromagnetic conductors, the main contributor to the magnetoresistance is the anisotropic magnetoresistance (AMR). It is now known that this is due to electron spin-orbit interaction which leads to a different electrical resistivity for a current direction parallel or perpendicular to the direction of magnetisation. When a magnetic field is applied, randomly oriented magnetic domains tend to align their magnetisation along the direction of the field, giving rise to a resistance change of the order of a few percent. The the AMR effect has been used for making magnetic sensors and read-out heads for magnetic disks. See also GMR

1857 Wheatstone introduced the first application of punched paper tapes (Ticker tapes) as a medium for the preparation, storage, and transmission of data (another one of Bain's ideas) which was rapidly adopted in the USA to speed up the transmission of Morse code.

1858 The laying of the first Transatlantic Telegraph Cable from two wooden warships, one of the greatest engineering feats of the nineteenth century, was completed. Financed by American entrepreneur Cyrus Field, it was designed and supervised by arrogant and incompetent amateur electrician Dr Edward Orange Wildman Whitehouse, a former surgeon from Brighton. Unfortunately the cable failed after less than a month in use, almost before the celebrations were complete, having transmitted only 732 messages. The signal pulses were generated from Daniell cells whose voltage was augmented using induction coils. In an attempt to solve the problem of weak signal levels Whitehouse, advised by Morse it is claimed, increased the battery voltage from 600 Volts to 2000 Volts with disastrous results causing the breakdown of the cable's insulation. Kelvin, a consultant on the project, had advocated solving the weak signal problem by using more sensitive receiving equipment. He had the same year patented a mirror galvanometer (originally devised by Poggendorff in 1826) which enabled the detection of very weak signals for this purpose which arch rival Whitehouse was reluctant to use, preferring his own detectors. Kelvin's work on this high profile project and his design and management of the subsequent successful cable laid in 1866 enhanced both his reputation and his bank balance as well as his already considerable ego.

It was not until 1956, almost a hundred years later, that the Atlantic was spanned by the first telephone cable TAT 1.

1858 German physicist Julius Plücker at Bonn University, looking for a way to observe "pure electricity" separate from the conductor carrying it, discovered cathode rays. Aware of Hauksbee's glow discharge demonstrations in 1705, he commissioned local glassblower Heinrich Geissler to construct an evacuated tube with a metal plate or electrode at each end. Plücker and his assistant Johann Hittorf evacuated the tubes using Geissler's "mercury air pump", which produced a much greater vacuum than Hauksbee had been able to achieve. They created an electric discharge between the electrodes and observed what happened in the intervening empty space. At first, with partial vacuum, the tube was filled with an eerie glow just as Hauksbee had found but as the vacuum was increased the glow disappeared and a different greenish glow appeared on the glass near one of the electrodes. Hittorf showed that the glow was due to invisible rays which he called glow rays (now called cathode rays) which were emanating from the other electrode. He noticed that they cast shadows when objects were placed in their way indicating that they travelled in straight lines and that they were deflected by magnets indicating that they were electrically charged.

On further investigation Plücker filled the tube with different rarified gases to observe how they conducted electricity and discovered that each gas glowed with a bright characteristic colour like modern day fluorescent lights, years before their time. Although this amazing nineteenth century invention was picked up by local shopkeepers to entertain their customers it was never commercialised and seems to have been forgotten until it was rediscovered by Claude in the twentieth century.

1858 Scottish linguist and chemist Archibald Scott Couper and German chemist Friedrich August Kekule von Stradonitz of Czech decent simultaneously and independently recognized that carbon atoms can link to each other to form chains giving birth to the study of organic chemistry. Prior to this thinking, it was believed that molecules could only have one central atom. Couper's publication was delayed for three weeks by his reviewer Charles Adolphe Wurtz and all credit for the discovery went to Kekule. Couper was devastated and never published another paper.

1858 The electric burglar alarm, invented five years earlier by Augustus Russell Pope, was first commercialised by American inventor Edwin Holmes who is usually credited with its invention. Holmes' workshop was later used by Bell in the development of the telephone and he was the first person to have a home telephone. Holmes' Burglar Alarm business was eventually bought by the American Telephone and Telegraph Company in 1905.

1858 Italian chemist Stanislao Cannizzaro, using Avogadro's theories, resolved the confusion between atoms and molecules of the compounds of the same atoms allowing a unified scale for relative atomic mass of the elements to be developed.

1859 Scottish engineer and polymath William John Macquorn Rankine published his "Manual of the Steam Engine and Other Prime Movers" in which he provided a systematic treatment of the theory of steam engines. Building on Carnot's theory on the efficiency of heat engines which was based on the thermodynamic cycle of a single gaseous phase reversible process, he recognised that the relationship does not apply if a phase change is encountered, because the heat added or removed during a phase change does not change the temperature of the working fluid. He therfore developed a more general theory of heat cycles for vapour based, closed systems in which the working fluid was alternately vapourised and condensed. Now known as the Rankine Cycle, it describes the steam cycle used in modern day electricity generating plants.

1860 The Lead Acid battery, the first practical rechargeable storage battery was demonstrated by Raymond Gaston Planté. It used spiral wound electrodes of Lead and Lead Oxide immersed in Sulphuric Acid and despite delivering remarkably high currents it remained a laboratory curiosity for two decades until the manufacturability and performance were improved by Fauré. The reversible battery cell chemistry had been observed 60 years earlier by Gautherot using copper electrodes but he failed to realise the potential of his discovery. (Sorry!) After over 145 years of development, patents are still being awarded for improvements to this simple device. Currently the value of Lead Acid batteries sold every year in the world is over $30 Billion and still growing.

1860 Concerned with the security of coal supplies, French mathematician Auguste Mouchout started work on the design of a solar powered motor, the first practical application of solar energy. The following year he was granted a patent for his design which used sunlight to boil water in a solar boiler to raise steam to drive a conventional motor. By 1865 his efficiency improvements included solar collectors or reflectors to catch and focus more of the sun's energy and also a tracking device to maintain the optimum orientation towards the sun.

1860 Maxwell showed that white light can be generated by mixing only three colours not the full spectrum as indicated by Newton.

The following year he published "On the theory of primary colours" in which he explained that any colour, not just white light, can be generated with a mixture of any three primary colours. He chose red, green and blue and produced the world's first colour photograph at a demonstration of colour photography to the Royal Institution in London in 1861. The subject was a tartan ribbon. Three separate monochrome images were made by exposing the ribbon through red green and blue filters respectively to make three lantern slides. A colour image of the ribbon was then created by projecting the three images from the slides simultaneously on to a screen through three separate lanterns, each equipped with the same filter used to make its image.

Maxwell also developed the colour triangle, a practical tool for generating any desired colour. The vertices of the triangle represent the primary colours and the proportions of each primary colour required to generate the desired colour are determined by the distance of the desired colour from each vertex.

Maxwell's work could be considered to be the basis for modern colorimetry. Colour television and HTML, the language used to generate the colours in Internet browsers, work on the principle of combining red, green and blue primary colours to produce the full spectrum of colours as proposed by Maxwell.

1861 German schoolmaster Johann Philipp Reis made the first public presentation of a working telephone to Frankfurt's Physics Association (Der Physikalische Verein) and published "Telephony Using Galvanic Current". His transmitter and receiver used a cork, a knitting needle, a sausage skin, and a piece of platinum. Initially fifty units were made but their performance was erratic. Unfortunately Reis suffered from tuberculosis and did not have the time nor the energy to perfect his invention which he called the "Telephon", nor did he find the time to patent it. He died at the age of forty.

1861 Italian immigrant to the USA, fugitive from persecution as a supporter of the Italian unification movement, Antonio Santi Giuseppe Meucci, after constructing numerous devices which enabled the transmission of sound, demonstrated a working telephone system in New York. It was based on a system he had devised for communicating between his bedridden wife's room and his workshop in the basement. He called it the Telettrofono and it was reported in the local Italian language newspaper "L'Eco d'Italia" at the time.

Meucci was perpetually short of cash. He was a prolific inventor but was unsuccessful in commercialising his ideas and this consumed most of his income. Nevertheless he also provided financial support to the leader of the Italian unification movement Giuseppe Garibaldi during his exile in the United States.

Meucci continued to devise improvements to his telephone system, including inductive loading (in 1870) to enable longer distance calls. Unfortunately, in 1871 when he was incapacitated with serious burns from an explosion aboard the steamship Westfield on which he was travelling, his wife sold all his early models of telephone devices for $6. Meucci could not afford the $250 needed to patent his system, however in 1871 he did manage to obtain a cheaper official "Caveat" stating his paternity of the invention. After the sale of the old prototypes, in 1874 he handed some new models to Western Union Telegraph for evaluation and these were subsequently seen by Alexander G. Bell who had access to the laboratory where they were stored. In 1876 he was surprised to read in the newspapers that Bell was credited as the sole inventor of of this amazing new device. United States Patent No. 174,465, issued to Alexander Graham Bell in 1876, became recognized as the world's "most valuable patent." Meanwhile Meucci died in poverty in 1989 bringing to an end the US Government's fraud proceedings against Bell.

Meucci was finally recognised as the first inventor of the telephone by the United States Congress in its resolution 269 dated June 15, 2002, 113 years after his death.

1863 The British government passes the Alkali Works Act setting limits to the emissions of noxious substances, one of the first attempts to recognise and control environmental pollution. Alkali compounds were widely used at the time in the production of glass, soap, and textiles and were manufactured using the Le Blanc Process whose byproducts included various harmful emissions including hydrochloric acid, nitrous oxides, sulphur and chlorine gas. As a result, manufacturing plants were ringed by dead and dying vegetation and scorched earth and local residents suffered health problems. The new law was backed by the appointment of Alkali Inspectors who monitored pollution levels.

One of the founders of modern chemical engineering was George E. Davis who started his career as an "Alkali Inspector". He stressed the value of large scale experimentation (the precursor of the modern pilot plant), safety practices, and a unit operations approach for controlling chemical manufacturing processes.

1863 Ányos Jedlik, then physics professor at the University of Pest in Hungary, introduced his multiplying capacitor battery in which a bank of electrostatic generators was used to simultaneously charge a parallel bank (battery) of capacitors. The charged capacitors were then switched to a series connection so that the voltage appearing on the output terminals was equal to the sum of the voltages on the individual capacitors, enabling very high voltages to be built up. He was awarded a gold medal at the 1873 Vienna World Exhibition for his design.

1864 Maxwell predicts that light, radiant heat, and "other radiations if any" are electromagnetic disturbances in the form of waves propagated through an electromagnetic field according to electromagnetic laws. It was not until 1873 that Maxwell provided the theoretical justification for his predictions.

1864 James Elkington the owner of a silver plating works in Birmingham, invented a commercial method for the refining of crude copper by the electrolytic deposition pure copper from a solution of copper salts. He patented the idea the following year and 1869 he founded the first electrolytic refining plant using this process, at Pembrey in South Wales.

1865 Clausius introduces the concept of entropy (from the Greek "transformation") defined as: "The internal energy of a system that cannot be converted to mechanical work" or "The property that describes the disorder of a system".

1865 The International Telecommunications Union (ITU), the world's oldest international organization, an example of international cooperation at its best, was established to develop a framework agreement covering the interconnection of the first national and independent telegraph networks which at the time were built and operated to different and often incompatible standards. Its agreements cover interconnections, signalling and message protocols, equipment standards, operating instructions, tariffs, accounting and billing rules.

Today every telephone whether it is a new push button phone or an old dial phone, an analogue or digital cordless phone, a mobile phone, a payphone or a proprietary office system phone can be connected to every other telephone in the world. The same network is used to connect fax machines and the telephone message may be analogue or digital. The telephone message may be routed to an office in New York, a remote rural village in China or it can find the called party wherever they might be driving their car in Europe, passing through open overhead wires, underground cables, microwave links, fibre optic links, satellite links, undersea cables or local wireless links on the way. The signalling will be understood, the message will get through and the intermediate organisations carrying the call will get paid for their service.

The telephone network used to be the biggest machine in the world. Now with the advent of the Internet it is even bigger with computers as well as telephones connected together over the same network with modems carrying data and broadband terminals passing data, video and a host of new services down the same old wires and it still all works thanks to the ITU working anonymously in the background.

1866 Almost thirty years after Davenport had built the first practical electric motor using electromagnets in both the stator and rotor, the same technique was applied to the self energising dynamo. A wound rotating electromagnetic armature, replacing the weaker permanent magnet of the magneto, was invented almost simultaneously by Samuel Alfred Varley who's design was patented on 12 December 1866, by Werner Siemens who publicised his design on 17 January 1867, and by Charles Wheatstone who presented a paper to the Royal Society on 4th February 1867 about the principles involved. The design permitted much more powerful and efficient DC generators.

It was later revealed that a patent had been granted in 1854 to Mr. Soren Hjorth, a Danish railway engineer and inventor for a similar invention with self excited armature coils. Hjorth's patent is to be found in the British Patent Office Library.

The principle had also been demonstrated by Hungarian priest Ányos Jedlik in 1861.

The advent of practical dynamos provided a convenient, low cost, inexhaustible source of electric power overcoming many of the limitations of the battery and marked the beginning of electricity generation by electromechanical means rather than by electrochemistry. Rotary generators paved the way for the widespread use of electricity for both high power industrial applications and for consumer appliances in the home.

1867 The reversibility of the dynamo was enunciated by Werner Siemens but it was not demonstrated on a practical scale until 1873 by Gramme and Fontaine.

1868 Invention of the Leclanché cell carbon-zinc wet cell by the French railway engineer Georges Leclanché. It used a cathode of manganese dioxide mixed with carbon contained in a porous pot and an anode of zinc in the form of a rod suspended in an outer glass container. The electrolyte was a solution of ammonium chloride that bathed the electrodes. The manganese dioxide acts as a depolariser absorbing hydrogen gas released at the cathode. The first practical battery product to be commercialised, it was immediately adopted by the telegraph service in Belgium and in the space of two years, twenty thousand of his cells were being used in the telegraph system. Later, it was also Alexander Graham Bell's battery of choice for his telephone demonstrations. Domestically however its use for many years was limited to door bells.

Leclanché's electrochemistry was implemented with a different cell construction by Gassner in 1886 to make more convenient dry cells which still survive today in the form of zinc-carbon dry cells, the lowest-cost flashlight batteries. Polaroid's PolaPulse disposable batteries used in instant film packs also used Leclanché chemistry although in a plastic sandwich.

1868 Maxwell analysed the stability of Watt's flyball centrifugal governor. Like Airy, he used differential equations of motion to find the characteristic equation of the system and studied the effect of the system parameters on stability and showed that the system is stable if the roots of the characteristic equation have negative real parts. He thus established the theoretical basis of modern feedback control systems or cybernetics.

1868 French engineer Jean Joseph Farcot patented improvements to machine control and in 1873 published a book entitled Le Servo-Moteur introducing the notion of servomechanisms which allow a small control system to control pieces of far heavier machinery.

1869 Prussian physicist Johann Wilhelm Hittorf published his laws governing the migration of ions. These were based on the concept of the transport number, the rate at which particular ions carried the electric current, which he had previously developed. He had noted in 1853 that some ions traveled more rapidly than others. By measuring the changes in the concentration of electrolyzed solutions, he computed from these the transport numbers (relative carrying capacities) of many ions.

1869 German chemist Julius Lother Meyer discovered the periodic relationship between the elements by plotting a graph of atomic weight against atomic volume, however its publication was delayed by the reviewer.

Working at the same time, this periodic relationship was also noticed by Russian chemist Dimitri Ivanovich Mendeleyev. By arranging cards with the names, atomic weights and some properties of the 65 known elements at that time, into rows and columns he noticed an underlying pattern. His Periodic Table of the elements was published before Meyer's and the Periodic Table thus became attributed to Mendeleyev. Since then over 700 versions of the table have been produced.

Gaps in the table led scientists to speculate on the existence of hitherto unknown elements with predicted properties related to their positions in the table. The existence and properties of these elements was duly confirmed once suitable experiments could be devised.

1869 French paper manufacturer Aristide Berges built the first hydroelectric generator at Lancey near Grenoble. Using sluice gates or penstocks, he directed water from a 200 metre high Alpine waterfall through a waterwheel which drove an electrical machine generating 1.5 kiloWatts of power. He coined the expression hydroelectric power. Over the years Berges built bigger machines and 1886-1887 he built the world's first hydraulic accumulator.

1870 New Yorker John Wesley Hyatt patented the first synthetic plastic, now called Celluloid, which was invented by Parkes in1855. He first used it as a coating for billiard balls and later for denture plates.

1870 John Player developed a process of mass producing strands of glass with a steam jet process to make what was called mineral wool for use as an effective insulating material. (Editor's Note - I have not yet been able to verify this first statement which could be an oft repeated internet myth related to the next paragraph. Please email me if you can help. The next statement is true.)

John Player had no connection with John Player cigarettes, a major brand in the 1980's. Nevertheless an unfounded rumour spread in the late 1980's and early 1990's, no doubt encouraged by their competitors, that the filters in John Player cigarettes contained fibreglass resulting in major damage to their market share.

1870's Austrian physicist Ludwig Eduard Boltzmann published a series of papers developing the theory of statistical mechanics with which he explained and predicted how the properties of atoms such as mass, charge, and structure determine the visible properties of matter such as viscosity, thermal conductivity, and diffusion. He showed that the kinetic energy of a molecule of an ideal gas is proportional to its absolute temperature. The ratio is equal to 1.38 X 10^-23 Joules per degree Kelvin (J/K) and is called the Boltzmann Constant in his honour.

Boltzmann also derived a theoretical relationships for the thermodynamic entropy of a gas. 70 years later Shannon used an equivalent relationship to define the information entropy in a message.

1871 Weber proposed the idea for atomic structure that atoms contain positive charges that are surrounded by rotating negative particles and that the application of an electric potential to a conductor causes the negative particles to migrate from one atom to another creating current flow.

1871 German scientist Steiner revived an apparently dead patient by passing a weak electrical current directly through his heart. The first recorded use of electric shock treatment for reviving people after cardiac arrest.

1872 PVC, Poly Vinyl Chloride first created by German chemist Eugen Baumann. It was not patented until 1913. In 1926 Waldo Semon invented a new way of making PVC into a useful product and he is now generally credited with discovering it.

1872 One of the many "Fathers of Radio" West Virginian dentist Mahlon Loomis was granted a patent for "a new and Improved Mode of Telegraphing and of Generating Light, Heat, and Motive Power". Although not a true radio system it was an attempt at making a wireless telegraphy system by replacing the batteries with electricity gathered from the atmosphere by means of flying kites attached to long copper wires. It used a Morse key between one kite wire and the ground to send signals and at the remote kite it used a galvanometer between the wire and the ground to detect the signals. It is claimed that signals using this method were transmitted over 14 miles, however it is questionable whether this system ever worked and it was never commercially exploited. Nevertheless the Guinness Book of Records credits Loomis with sending the first signals through the air. It was another sixteen years before Hertz demonstrated the existence of radio waves.

1872 American telecommunications engineer Joseph Barker Stearns of Boston developed the first practical telecommunications duplexing system. He accomplished this by using two different types of signals, one for each direction. In one direction he used varying strength signals (e.g. On or Off) which he detected with a common or neutral relay, while in the opposite direction he used varying polarity signals (Plus or Minus) which he detected with a polarised relay. The receivers were designed to respond only to signals of the appropriate type from the remote transmitter and to ignore local transmissions. Stearns' system effectively doubled the capacity of the installed telegraph lines and Western Union rapidly acquired rights to use it.

1872 British electrical engineer Josiah Latimer Clark invented the Clark Standard Cell which provided a reference voltage of 1.434 volts at 15 °C. The cathode was Mercury, in contact with a paste of Mercurous Sulphate, and the anode was Zinc amalgam in contact with a saturated solution of Zinc Sulphate.

1873 Scottish physicist James Clerk Maxwell published his "Treatise on Electricity and Magnetism" in which, using a water analogy, he distilled all electromagnetic theory into a set of four rules now accepted as one of the fundamental laws of nature. Now known as Maxwell's Equations, they were one of the most important scientific works of the century, not only explaining all electric, magnetic and radiation phenomena known at the time but also providing the foundations for the two great theoretical advances of the twentieth century, relativity and quantum theory.

In mathematical vector form these complex relationships can be expressed very simply as:-

∇• D = ρ

∇• B = 0

∇x H = J + δD/δt

∇x E = - δB/δt

Where
ρ is the free electric charge density (not including dipoles)
D is the electric displacement field or flux density
B is the magnetic flux density
H is the magnetic field
J is the current density
E is the electric field
∇• is the divergence operator
∇x is the curl operator

These four equations provided the theoretical justification of his 1864 predictions of the existence of radiation or electromagnetic (radio) waves, even though at that time there was still no evidence to demonstrate it.

Maxwell showed that electromagnetic fields hold energy which is in every way equivalent to mechanical energy and that a changing magnetic field will induce a changing electric field which in turn induces a changing magnetic field, and so on, such that an electromagnetic wave is created in which the energy oscillates between the electric and magnetic fields.

He also showed that neither the electric wave nor the magnetic wave can exist alone. They travel together, always at right angles and in phase with eachother.

The velocity of propagation of the electromagnetic wave v can also be derived from Maxwell's equations as v = E/B the ratio between the electric field strength E and magnetic flux density B which is also equal to 1/√µ₀ε₀ where µ₀ and ε₀ are the magnetic permeability and the electric permittivity of a vacuum. From a knowledge of the magnitudes of >µ₀ and ε₀ he determined that the velocity of propagation of the electromagnetic wave is constant and equal to the speed of light and that light is an electromagnetic wave.

It is a measure of Maxwell's genius that with four elegant and concise equations he could not only account for the movement of a compass needle next to a current carrying wire but with the same equations he was also able to predict, understand and correctly characterise mathematically such a complex phenomenon as electromagnetic radiation that nobody had yet witnessed or even imagined.

Maxwell was initially encouraged and supported in his theories by Kelvin, upon whose earlier work he built, however in his lifetime Kelvin never accepted Maxwell's conclusions believing them too theoretical and not related to reality.

It was 1888 before his predictions were proved right by experiments carried out by Heinrich Hertz.

In the twentieth century, while Einstein's relativity theory required Newton's laws to be modified, Maxwell's equations remained absolute.

Maxwell also introduced statistical methods into the study of physics, now accepted as commonplace and made significant contributions to structural analysts, feedback control theory (cybernetics) and the theory of colour taking the first ever colour photograph.

Maxwell was a kind and modest man, universally liked. His ideas were ahead of his time but he made no attempt to promote his work. Despite his monumental achievement, it was Hertz' name rather than Maxwell's that has become associated with radio waves and radio propagation.

Maxwell died of stomach cancer in 1879 at the age of forty eight without seeing the experimental confirmation of his theories.

When Michael Faraday was asked what was his greatest ever discovery he replied "James Maxwell"

"The Special Theory of Relativity owes its origins to Maxwell's Equations of the Electromagnetic Field" - Albert Einstein.

"Ten thousand years from now, there can be little doubt that the most significant event of the 19th century will be judged as Maxwell's discovery of the laws of electrodynamics" - Richard Feynman

1873 Belgian carpenter and instrument maker Zénobe Théophile Gramme in partnership with French engineer and inventor Hippolyte Fontaine developed the first reliable commutators for DC machines. (The commutator is the device which reverses the current in the rotor coil as it passes from the influence of one magnet pole to the next magnet pole of opposite polarity in order to maintain a unidirectional current in the external circuit).

They also demonstrated the reversibility of their dynamo by pumping water at the Vienna International Exhibition using two dynamos connected together, one, the generator, deriving motion from a hydraulic engine, provided electrical power to the receiving dynamo which worked the pump. It is said that they discovered the phenomenon by accident when an idle dynamo was mistakenly connected across another working/running dynamo and began motoring backwards. They did however realise that the importance of their discovery was not just the reversibility of the dynamo, but also the possibilities electrical power transmission. The fact that electrical power could be generated in one place and used in another.

1873 The first demonstration of electric traction in a road vehicle by Robert Davidson in Edinburgh using iron/zinc primary cells to drive a truck.

1873 English telegraph engineers, Joseph May and Willoughby Smith, while working with Selenium, noticed that its conductivity changed under the influence of light thus discovering the photoconductivity effect.

1873 Dutch physicist Johannes Diederik van der Waals deduced more accurate gas laws taking into account the volume of the actual molecules making up the gas and the intermolecular forces between them. The van der Waals forces, named after him, assumed that neutral molecules behaved like dipoles with a positive charge on one side and a negative charge on the other because their shape was distorted. The true nature of the forces was later explained in 1930 by Polish-born physicist Fritz London using quantum theory.

Van der Waals was awarded a Nobel Prize in 1910 for his work on the equation of state for gases and liquids.

1874 A thermo-electric battery based on the Seebeck effect powered by a gas heater introduced by M Clamond in France. Known as the Clamond pile or thermopile, it consisted of a stack of circular arrays of junctions of iron with a zinc-antimony alloy heated by a gas burner located in the centre of the stack. It generated 8 Volts providing a current of 2 to 3 Amps and supplied both heat and electricity to galvanising baths.

1874 Thomas Alva Edison invented the quadruplex telegraph, which was capable of sending four Morse coded messages simultaneously on a single channel. He amalgamated and rearranged the duplexer of Gintl, and Farmer and the diplexer of Stearns into a single system permitting two messages to be sent in each direction. As with Gintl's duplexer design, two relays in each terminal were unresponsive to outgoing signals, one of these relays responded to current increases of the incoming signals the while the other responded to current reversals of the received signals. Thus Stearns duplexing method of distinguishing between two signals was modified by Edison to separate the signals going in the same direction (diplexing) rather than in opposite directions (duplexing). This avoided the problem of synchronising the receivers with the transmitters. The quadruplex allowed the telegraph lines to carry four times the traffic and saved the telegraph companies millions of dollars.

Edison had started the development of his quadruplex system in 1873 in cooperation with Western Union using their facilities for his experimental work. He had agreed with William Orton, the president of Western Union, a development fee and that the patents for the design would be assigned to Western Union. When the design was complete Edison was given $5000 as part payment and $25,000 later. Orton also authorised a royalty payment to Edison of $233 per year before leaving on a business trip. While he was away, Edison was approached by George Jay Gould, railroad baron, Wall Street financier, stock manipulator and head of Atlantic and Pacific Telegraph Company, an arch rival of Western Union. He offered Edison $30,000 cash for the quadruplex patents and a job at Atlantic and Pacific. Edison accepted and wrote to Orton saying their arrangement had been a mistake and he revoked the assignment of patents to Western Union. Edison had sold the patents twice over. There followed years of litigation which only ended with the eventual amalgamation of the two telegraph companies. A portent of Edison's business methods to come. See Edison and Tesla.

Quadruplex telegraphs were eventually displaced by two new inventions, Baudot's multiplex telegraphy capable of eight or more simultaneous transmissions (see next) and Murray's teleprinter machines which did not use Morse code.

1874 Jean Maurice Émile Baudot, an officer of the French Telegraph Service made major improvements in the telegraph system by bringing together the five unit code devised by Gauss and Weber, now called the five bit Baudot code, and the synchronous time division multiplex (TDM) system, proposed by Farmer in 1852, into a practical design for a printing telegraph.

The five bit code was the first truly digital code, each unit having only two logical states, giving 32 possible combinations or characters, the shortest practicable code for the number of characters to be transmitted. Baudot used two special characters to switch between letters and numbers giving effectively 64 combinations, enough to allow for 26 characters for the alphabet and 10 numbers plus other miscellaneous punctuation and synchronisation codes. Input was by 5 keys. Later adaptations by Murray in 1903 (and others) used five hole punched tape to input the characters with a sixth row of smaller holes to feed the tape through the reader. The tape had the advantage that it could be punched off line and subsequently transmitted at high speed, but more importantly the tapes enabled the transmission speed to be controlled thus facilitating the multiplexing. Early teletypewriters also used Baudot code which eventually supplanted Morse code as the most commonly used telegraphic alphabet becoming known as the International Telegraph Code No.1.

Although the code is now named after Baudot, the five digit binary code was first proposed by Francis Bacon in 1605.

The Baudot distributor enabled four messages to be transmitted simultaneously. Multiplexing was achieved by using synchronised motors at either end of the line with brushes which connected each channel sequentially, for a fixed interval, to a single transmission line as the motor rotated. Synchronisation codes were sent down the line to keep the transmitter and receiver in step.

In modern circuits TDM is accomplished by interleaving the bit streams from the different channels.

The unit of measurement for data transmission rates of one character per second is named the Baud, a shortened form of Baudot, in his honour.

1874 German physicist Karl Ferdinand Braun discovered one way conduction in metal sulfide crystals. He later used the rectifying properties of the galena crystal, a semiconductor material composed of lead sulfide, to create the crystal detector used for detecting radio signals which Braun worked on with Marconi. Thus was born the first semiconductor device. Now called the diode, the cat's whisker detector was rediscovered and patented 30 years later by Pickard and Dunwoody.

1874 Irish physicist George Johnstone Stoney expanding on Faraday's laws of electrolysis and the notion that an electric charge was associated with the particles deposited on the electrodes during electrolysis, proposed that the minimum unit of charge was that which was found on the hydrogen ion and that it should be a fundamental unit. He named it the "electrine". In 1891, he changed the name to "electron". He calculated the magnitude of this charge from data obtained from the electrolysis of water and the kinetic theory of gases. The value obtained later became known as a coulomb. Stoney was unaware of the nature of the atom and "Stoney's electron" is a unit of charge, not to be confused with J.J. Thomson's sub atomic particle which Thomson called a corpuscle but which we now call the electron.

1874 David Salomons of Tunbridge Wells, England demonstrated a 1 H.P. three wheeled electric car powered by Bunsen cells.

1875 American physicist Henry Augustus Rowland was the first to show that moving electric charge is the same thing as an electric current.

He built up an electrostatic charge on a rotating gramophone (phonograph) record by rubbing it with woolen cloth. A magnetic compass bought in close to the spinning disk was deflected, the magnitude of the deflection increasing with the speed of the disk. This showed that a magnetic field is not only set up by a current moving through a wire but also by a moving electrostatic field.

1876 On March 10 in Boston, Massachusetts, Alexander Graham Bell, a Scottish emigré to the USA, invented the telephone. Bell filed his application just hours before his competitor, American inventor Elisha Gray, founder of Western Electric, filed notice with the same patent examiner, an outline of a telephone he planned to patent himself. What's more, neither man had actually built a working telephone. Bell in particular did not have a working microphone but he made his telephone operate three weeks later using the microphone described in Gray's Notice of Invention, and methods Bell did not propose in his own patent. Being a "system" using several technologies over which Bell claimed sole rights, it spawned more than 600 law suits mostly focused on whether the concept of modulating a DC current supplied by a battery was revolutionary or insubstantial and which of the many rivals had thought of it first. Legitimate claimants included Belgian experimenter Charles Bourseul (1854), German schoolmaster Johann Philipp Reis (1861) and impoverished Italian US immigrant Antonio Meucci (1861) to whom the idea is now officially credited by the American Congress (disregarding the prior work of Reis).

Bell's United States Patent No. 174465 became recognized as the world's most valuable patent.

Similar controversies surround the invention of radio, but that's another story.

In an attempt to find an assassin's bullet lodged in the body of US President James Garfield, in 1881Bell hastily devised a crude metal detector based on the induction balance recently devised in 1879 by David Hughes. It worked but it didn't find the bullet, indicating that it was deeper than at first thought. It was later discovered that the detector had been confused by the newly invented metal bed springs under the mattress on which the President lay. (The President died after eighty painful days from complications arising from contamination of, and further damage to his wound by the dozen or more doctors probing his body in search of the bullet).

In later life Bell moved to the relative seclusion of his estate in Nova Scotia where he declared himself to be sick of the telephone which he regarded as a nuisance, referring to it as a "beast". He crusaded tirelessly on behalf of the deaf and worked on a variety of projects including flight and aerofoils. At odds with his genuine concern for the deaf, he was an advocate of eugenics and carried out experiments with sheep. He was convinced that sheep with extra nipples would give birth to more lambs, and built a huge village of sheep pens, spending years counting sheep nipples, before the US State Department announced that extra nipples were not linked with extra lambs.

1877 The telephone industry created the next major leap forward in the demand for batteries.

In Bell's original 1876 system the microphone was a passive transducer in which the acoustic power of the human voice provided the energy to create the varying electric currents which represent the sound and also to carry them down the wire to the receiver. In Bell's microphone, or transmitter in telephone parlance, sound waves impinge upon a steel diaphragm causing it to vibrate in sympathy. The diaphragm is arranged adjacent to the pole of a bar electromagnet and acts as an armature. The vibrations of the diaphragm cause very weak electrical impulses to be induced in the coil of the electromagnet. However these feeble signals were quickly attenuated as they passed down the telephone line until they were inaudible, severely limiting the range of the circuit and hence the potential of the telephone system.

During 1877 and 1878 German born American Emil Berliner, David Hughes, Thomas Edison, Bell employee Francis Blake and English curate Henry Hunnings, were each working independently on designs for improved microphones based on active transducers in which the acoustic power controls an external source of power. An active transducer provides an electrical signal with about a thousand times more electrical power than the acoustical power absorbed by the transducer and their designs considerably improved the range of the telephone at the expense of requiring power from a local battery. They all used variants of a carbon transducer which depend on the fact that the electrical resistance of some materials varies with the physical pressure exerted on it, various forms of carbon material, such as carbon granules, coke or lamp black being particularly sensitive. In the carbon microphones which they developed, during the call the battery current flows constantly in a closed circuit across a capsule of carbon material between two terminals one of which is a flexible diaphragm. The sound pressure variations are transferred to the carbon by the diaphragm thus causing the battery current to vary in response to the sound pressure. Edison's design used lamp black and had the added refinement of an induction coil or step up transformer which superimposed the sound information from the transducer on to a separate higher level DC current flowing through the secondary winding of the coil in the main transmission line so that an amplified signal appeared across the terminals of the secondary coil and the stronger DC current carried it further. A process we now call modulation.

Rather than patenting his ideas for the microphone, Hughes, who was already wealthy from his invention in 1855 of the printing telegraph, communicated his designs to the Royal Society in the February 1878 and generously gave the carbon microphone to the world. This earned him the wrath of Thomas Edison who laid claim to the invention, accusing Hughes of plagiarism and patent infringement. Two months later Berliner and Edison filed for patents on carbon microphones within two weeks of each other resulting in numerous bitter law suits which were eventually settled out of court. Hunnings patented the idea of using carbon granules which could carry higher currents but his patent was challenged by Edison's lawyers. Being a man of limited means he conceded and sold the rights for £1000 and went on Edison's payroll. Berliner went to work for Bell who bought his design for $50,000 and Edison's design, based on principles described by Hughes but using Hunnings' crushed carbon granules became the basis of the standard telephone transmitter and with a few refinements was used for over a hundred years.

Berliner went on to found Deutsche Grammophon Co. and his trademark image became a painting by English artist Mark Barraud of his dog "Nipper" listening to His Master's Voice for which Barraud was paid £50 for the painting and a further £50 for the full copyright. Berliner's other notable invention was the gramophone using a flat disk instead of the cylinder used by Edison.

1877 English experimenter Williams Grylls Adams and his student Richard Evans Day discovered that an electrical current could be created in Selenium solely by exposing it to light and produced the first Solar Cells naming the currents produced this way photoelectric. Although the effect was attributed to the properties of Selenium it was in fact due to the properties of the junction between the Selenium, now known to be a semiconducting material, and the Platinum metal used to create the connection for measuring the current.

Note: Confusingly the currents produced by solar cells, named photoelectric currents by Adams and Day, do not arise from the photoelectric effect in which light causes electrons to be emitted from the surface of the material by the process of photo-emission. Solar cells or photovoltaic cells are made of semiconductor material. The incoming light (photons) moves electrons from the valence band across the band gap to the conduction band and the resulting electron-hole pairs cause an internal electrical field to be set up across the P-N junction which separates them. In this way different charges on the two electrodes of the solar cell are created, and this potential difference can be used to drive a current through a wire.

It was not until 1954 that the efficiency of photovoltaic cells was improved enough to generate useful power.

1877, German, Ernst Siemens patented the first loudspeaker before the advent of electrical music reproduction.

1878 American physical chemist Josiah Willard Gibbs developed the theory of Chemical Thermodynamics introducing the free energy concept. When a chemical reaction occurs, the free energy of the system changes. The free energy is the amount of energy available to do external work, ignoring any changes on pressure or volume associated with the change of state. Thus the change in Gibbs free energy represents the total useful energy released by the chemical action which can be made available for doing work. When the free energy decreases, the entropy always increases, and the reaction is spontaneous. (The value of the free energy lies in the fact that its change is easier to measure than the change in entropy.)

He also developed fundamental equations and relationships to calculate multiphase equilibrium and the phase rule which specifies the minimum possible number of degrees of freedom, or variables such as temperature, pressure, concentration etc. in a (closed) system at equilibrium which must be specified , in terms of the number of separate phases and the number of chemical constituents in the system, in order to completely describe the state of the system. Gibbs' work laid the foundations for the theoretical representation of the energy transfers involved in chemical reactions. This allowed the performance (energy release) of galvanic cells to be quantified and predicted.

He published his work in the Transactions of the Connecticut Academy of Arts and Sciences, an obscure publication, published by his brother in law, with a very limited, mostly local, circulation. His work on thermodynamics, a major advance in the understanding of chemical reactions, therefore remained unknown until 1883, when Wilhelm Ostwald a Russian-German physical chemist discovered it and translated it to German.

In 1881 Gibbs published "Elements of Vector Analysis" which presents what is essentially the modern system of vector analysis. It permitted the presentation and analysis of complex relationships between multi-dimensional forces such as Maxwell's field theory to be simplified by the use of Gibbs' vector notation and methods. He also made important contributions to the electromagnetic theory of light. His later work on statistical mechanics was also important, providing a mathematical framework for quantum theory.

For all his major contributions to science, Gibbs was a modest man like Maxwell who shunned fame and fortune, living a quiet and contented, simple life as a bachelor, much admired by his students at Yale where he worked.

1878 French electrician, Alfred Niaudet, published "Traité élémentaire de la pile électrique" on electric batteries in which he described over a hundred different battery types and combinations of elements, indicating the growth and importance of battery technology.

Niaudet described the various chemical mixes and designs which had been used to address a range of design goals. The polarisation problem was solved by using non polarising chemical mixes which did not produce gases, or by using mixes which included depolarising agents or oxidants, which reduced any hydrogen emissions by combination with oxygen. Other recipes were used to achieve higher cell voltages, higher capacity, lower costs or longer life. Alternative constructions were designed to improve the convenience of use and current carrying capability or to reduce the cell's internal resistance. Later the possibility of electrical recharging became a design aim.

Non polarising 2 Volt primary cells were mostly based on potassium dichromate and often used two electrolyte gravity cells (See below). Examples were:

Potassium dichromate is strongly toxic and these cells consequently fell into disuse.

Gravity cells are two electrolyte cells which depend on a lighter electrolyte, such as zinc sulphate, floating on the top of a heavier electrolyte, such as copper sulphate, like oil and water. Normally, diffusion would soon mix the two liquids destroying the cell's efficacy, but if a current was drawn continuously the natural migration of the ions kept the electrolytes apart. This construction reduced the internal resistance of the battery by eliminating the porous pot from the current path. Gravity cells were used extensively in the telegraph and telephone industry, however the inconvenience of keeping the cells undisturbed to avoid mixing the electrolytes and also above freezing temperatures eventually led to their replacement.

Gravity cells which used zinc electrodes suspended in zinc sulphate or sulphuric acid were also called Crowfoot Cells because the shape of the zinc electrode resembled the bird's foot.

Other non polarising primary cells such as the Daniell cell were two electrolyte cells based on copper sulphate and sulphuric acid electrolytes. These included designs by the following inventors

These cells all produced only 1 Volt which made them less attractive than the 2 Volt dichromate cells.

Many batteries at that time used elemental mercury for contacts or for preventing local action at the zinc electrodes. Impurities in zinc, such as iron or nickel, effectively created minute short-circuited cells around each grain of impurity which soon ate away the zinc. Pure zinc was far too expensive to be considered at that time, however in 1835 William Sturgeon discovered that the local action in the cheaper impure zinc could be eliminated if the zinc electrodes were amalgamated with liquid mercury.

In 1840 Sturgeon developed a long lasting battery consisting of a cast iron cylinder into which a rolled cylinder of amalgamated zinc was placed. Discs of millboard were used as separators and the electrolyte was dilute sulfuric acid.

Depolarising cells from the same period were usually based on nitric acid with a cell voltage of 1.9 Volts and included:

Although these cells were popular, the acid decomposed rather than polarising the cell giving off toxic nitric dioxide gas which eventually led to their demise.

All of the above cells were primary cells, but most were designed for re-use. In general, they used aqueous electrolytes enclosed in stout containers, often made of glass. Once the cell was discharged the spent chemicals could be replaced or replenished: - a form of mechanical recharging. High volume users such as the telegraph and telephone companies pioneered recycling, working with their battery suppliers to reprocess and recover expensive elements from the used electrolytes. (In 1886 Western Union recovered 3000 pounds of copper in this way.)

A further impetus was given to the search for alternative chemistries after 1860 when Gaston Planté demonstrated the feasibility of rechargeable cells with his Lead Acid battery.

All of the above primary cells were eventually superceded for PTT use by versions of Planté's rechargeable battery or by mains power.

For portable power, the Leclanché cell was one of the few surviving primary cells from this period.

1878 In a letter sent to the publication "Mechanic and World Science" Irish experimenter Denis D. Redmond described a 10 by 10 array of Selenium photocells each connected to a corresponding array of platinum wires which would glow when light impinged on the photocells. The system was the first to provide electric transmission of moving images, albeit silhouettes, only one year after the discovery of the photovoltaic effect and one year before Edison patented his light bulb. The system had no image scanning (later provided by Nipkow) so it required 100 channels to transmit the image. Nevertheless it was the forerunner of the modern television system.

The same year Portuguese professor Adriano de Paiva published "La téléscopie électrique basée sur l'emploi du sélénium" in a Portuguese publication "Commercio Portuguez", curiously written mostly in French with some Portuguese. It described a similar system to Redmond's which he called an electric telescope anticipating a different application from what eventually transpired.

It was another five years before practical photovoltaic cells were invented by Fritts.

1879 American physicist Edwin Herbert Hall discovers that when a solid material carrying an electric current is placed in a magnetic field perpendicular to the current, a transverse electric field is created in the current carrier. Known as the Hall Effect in his honour. The voltage drop across the conductor at right angles to the current is called the Hall Voltage and is proportional to the external magnetic field. Now used in sensors for measuring magnetic field strength.

1879 The invention which did more than any other to promote the use of electricity in the home, the electric light bulb was patented by Thomas Alva Edison. In the early years however the only source of domestic electrical energy generally available was the battery and so all the development took place using DC/battery power.

History is written by the winners and a certain mythology has built up around Edison's inventive genius. The light bulb itself is synonymous with bright ideas but also with Thomas Edison himself. Forgotten however is English experimenter William de la Rue's 1920 incandescent lamp using a platinum filament in a partially evacuated glass tube. Forgotten also are all the previous patents for electric lights similar to Edison's using carbon filaments in evacuated bulbs or bulbs filled with inert gas. These included American John W Starr from Cincinnati who was granted a UK patent in 1845 for a carbon filament incandescent lamp which he successfully demonstrated to Michael Faraday. Unfortunately Starr was found dead in bed the day after the demonstration at the age of 25, it is said, of "excitement and overwork of the brain" and nothing further became of his invention. Forgotten too are the similar inventions of Alexander Lodygin in Russia (1872), Henry Woodward and Matthew Evans in Canada (1874) and Joseph Swan in the England who demonstrated an almost identical lamp to the Newcastle Literary and Philosophical Society eight months before Edison's "breakthrough". Edison actually sued Swan for patent infringement and the matter was finally settled out of court when the rivals formed the Edison and Swan United Electric Company.

Considering that Edison's name is almost synonymous with the invention of the light bulb it is perhaps surprising to note that in 1883 the US Patent Office ruled that a prior invention patented in 1878 by William Sawyer and Albon Man took precedence.

Despite the unfortunate ending to their previous relationship, in 1877 Edison was hired once more by William Orton the head of Western Union to try to break Bell's patents on the telephone. Orton is quoted as saying that "Edison had a vacuum where his conscience ought to be". The battlefield was to be the telephone transmitter where Bell's design was inadequate but several others were already working on this. Edison provided an innovative design but it also used ideas developed by others and Edison's rights to these were only settled after litigation. He was paid over $100,000 for his solution by Western Union and this gave him the funding and the independence he needed to develop his creative talent. (Bell's lawyers later successfully overturned Orton's main patent challenges to Bell's system although Edison's patents on the carbon microphone were upheld.)

Edison made his first patent application in 1868 when he was 21 years old and over his lifetime he was granted 1,093 U.S. patents including 106 in 1882. In addition he also filed an estimated 500-600 unsuccessful or abandoned applications. This amounts to two successful patents per week during his most productive period and a patent application on average every eight working days over his long working lifetime of sixty years. Considering that three of these inventions, the light bulb, the phonograph and the movie projector for which he is famous each took several years of development, and at the same time he had a large company to run, you have ask your self how much Edison himself contributed to the patents which bear his name.

Canadian author Peter McArthur is quoted as saying in 1901 "Every successful enterprise requires three men: a dreamer, a businessman and a son-of-a-bitch". The giants of the industry seem to embody all three of these characteristics at the same time.

The story of the light bulb is a re-run of the telegraphy and telephony stories, intrigues destined to be repeated with radio, computers, the internet and each new technology advance.

1879 Repeating the 1858 experiment of Plücker and Hittorf Sir William Crookes used a Geissler vacuum tube with an anode in the shape of a cross noticed that the cross cast a shadow on a zinc sulfide fluorescent coating on the end of the tube. He hypothesized that there must have been rays coming from the cathode which caused the zinc sulfide to fluoresce and the cross to create a shadow. He called these rays cathode rays. Crookes tubes were used by Röntgen in 1895 to demonstrate X-rays and by J. J. Thomson in 1897 in his discovery of the electron.

Crookes also invented the radiometer which detects the presence of radiation. It consists of an evacuated glass bulb in which lightweight metal vanes are mounted on a low friction spindle. Each vane is polished on one side, and blackened on the other. In sunlight , or exposed to a source of infrared radiation (even the heat of a hand nearby can be enough), the vanes turn with no apparent motive power.

Crookes was a believer in the occult and in the 1870's claimed to have verified the authenticity of psychic phenomena. He was knighted by Queen Victoria who, it is rumoured, had similar interests.

1879 Siemens Halske demonstrate an electric railway at an exhibition in Berlin. Power was provided from a separate generator which supplied the train via a third rail. A similar system was built in 1883 to run a commercial service along Brighton promenade in the UK by the son of a German clockmaker, Magnus Volk, an electrical engineer who had already completed the electric lighting of Brighton Pavilion. It was the world's first publicly operated electric railway when it opened and with some modifications his trains are still carrying passengers along the promenade today.

1879 Austrian physicist Josef Stefan formulated a law which states that the radiant energy of a blackbody is proportional to the fourth power of its temperature.

1879 After five years working as music professor, Welsh born American David Edward Hughes resigned in 1855 to patent a printing telegraph which became very successful in the USA and most of Europe, except Great Britain, bringing him international honours. In 1879 he invented the induction balance, the basis of the metal detector. It consists of two coils, one transmitting a low frequency signal and one connected to a receiver (detector) arranged in such a way that the receiver coil is close to, but shielded from, the transmitter coil so that in free space it does not pick up (detect) any signals from the transmitter. When the coils are brought near to a metal object, small perturbations in the magnetic field upset the balance between the coils causing a current to flow in the receiving coil thus indicating the presence of the metallic object.

The same year while working on his induction balance he noticed a clicking in a separate home made telephone ear-piece. He diagnosed this to be caused by a loose wire in his induction balance since the clicking stopped when the wire was firmly connected. He deduced that invisible waves, which he called aerial transmissions and which would today be called radio waves, were being emitted from a spark gap which occurred when the wire in the transmitting coil of the induction balance became disconnected and that the ear piece was picking them up. Investigating further he devised a clockwork device for opening and closing the spark gap and was able to pick up signals from the spark gap with his telephone receiver over ever greater distances, up to 500 yards, walking up and down Great Portland Street in London. Effectively he made the world's first mobile phone call. In 1880 Hughes demonstrated the phenomenon to the Royal Society in London but the president, mathematician William Spottiswoode was not impressed. According to George Gabriel Stokes, Irish mathematician and physicist specialising in hydraulics and optics, who witnessed the demonstration, the phenomenon was explained by induction not radio waves. Discouraged, Hughes passed on to other interests and did not pursue his discovery. Eight years later Hertz was credited with the discovery of radio waves.

1880 the brothers Pierre Curie and Jacques Curie predicted and demonstrated piezoelectricity.

1880 Emile Alphonse Fauré in France patented pasted plates for manufacturing lead-acid batteries. The lead plates were coated with a paste of lead dioxide and sulphuric acid which greatly increased the capacity of the cells and reduced the formation time. This was a significant breakthrough which led directly to the industrial manufacture of lead-acid batteries.

1880 Herman Hammesfahr, a German immigrant to the USA, was awarded a patent for a durable and flame retardant fibreglass cloth with the diameter and texture of silk fibres. He showed a glass dress at the 1893 Chicago World Fair. (Also attributed to American glass manufacturer Edward Drummond Libbey founder of Owens-Illinois).

1881 Improvements to the Leclanché cell, to avoid leakage, by encapsulating both the negative electrode and porous pot into a sealed zinc cup were patented by J.A. Thiebaut.

1881 The first electric torch or flashlight patented by English inventors Ebenezer Burr and William Thomas Scott. The original lamps were designed as portable table lamps and powered by a wet cell battery in a waterproof box. At the time the first power station had not yet been commissioned and there were no households wired up for mains electricity. More convenient portable versions of the torch using the recently invented dry cells were introduced starting in 1883. They quickly became popular for bicycle and miners lamps.

1881 Lead acid rechargeable batteries were first used to power an electric car by M. G. Touvé in France.

1881 The first International Electric Congress or International Conference of Electricians convened in Paris to define the international terms for the electrical units of electromotive force (Volt), resistance (Ohm), current (Ampère) The Congress also specified the manner and conditions in which the units were to be measured. Up to this time there had been at least twelve different units of electromotive force, ten different units of current, and fifteen different units of resistance.

The standard Ohm was defined by the resistance of a specified column of mercury, the standard Ampère by the current which deposits metallic silver at a specified rate from a silver nitrate solution and the standard Volt was defined by the EMF produced by an electrical circuit passing through an electrical field at a specified rate. However since most laboratories were not equipped to generate a standard Volt in the specified manner, and in any case they used batteries to provide their source of electric potential, a new voltage standard was devised, based on the EMF produced by a standard Clark cell and this was adopted at the fourth International Electric Congress in Chicago in 1893. Unfortunately with the three standards each based on independent measured quantities, Volts did not always equal Amps multiplied by Ohms and the voltage standard had to be changed once more. The 1908 International Congress in London consequently changed the Volt to a derived unit based on the standard Ampère and standard Ohm.

1881 American engineer Frederick Winslow Taylor working at the Midvale Steel company introduced Time and Motion Studies or Work Study and Method Studies to streamline manufacturing and eliminate unnecessary work. They enabled major efficiency savings to be made and became the foundation of Scientific Management.

1881 Patent granted to William Wiley Smith for the induction telegraph used to communicate with moving trains. Soon afterwards improved versions were invented independently by Lucius J. Phelps (1884), Edison (1885) and black American Granville T, Woods (1887). The system consisted of a track-side wire or rail which could pick up signals from an induction coil mounted on the train, essentially acting as the primary and secondary windings of a transformer. The forerunner of the mobile phone.

Similar systems, based on the same principle, were also used for fixed wireless communications before the discovery of radio (Hertzian) waves.

1882 French physicist and physician Jacques Arsène d'Arsonval invented the moving coil galvanometer. It had shaped pole pieces which enabled it to have a linear scale and became the basis of all modern electromechanical analogue panel meters.

1882 Nikola Tesla, working in Budapest, identified the rotating magnetic field principle and the following year used it to design a two-phase induction motor.

1882 French chemists Felix de Lalande and Georges Chaperon introduce the first battery to use alkaline electrolyte, the Lalande-Chaperon cell, the predecessor of the Nickel-Cadmium cell. Using electrodes of Zinc and Copper Oxide with a Potassium Hydroxide electrolyte, it was rechargeable and produced a voltage of 0.85 Volts.

Up to that point, all batteries had used acidic electrolytes. They chose to investigate alkaline rather than acidic electrolytes because electrodes of most metals and their compounds are attacked by the acid. Lead is one of the few metals resisting the acids but it is very heavy and a weight savings would be secured by using almost any other metal.

1882 English amateur scientist James Wimshurst invented the Wimshurst Electrostatic Generator, the first machine capable of generating high voltage static electricity that was unaffected by atmospheric humidity. Static electrical charges of opposite polarity built up on its two fourteen and a half inch (38 cm) contra-rotating discs sufficient to draw a four and a half inch (12 cm) spark. Since the breakdown voltage for air is 30,000 Volts per centimetre, this small table top machine was capable of generating over 300,000 Volts. As a reliable source of high voltage electricity, it not only provided a practical power source for X-ray machines, but it was a boon to Victorian experimenters enabling them to carry out serious scientific investigations or to carry out dubious experiments in electrotherapy. Wimshurst's basic design is still used in electrical laboratories today.

1882 Ayrton and Perry in England build an electric tricycle with a range of 10 to 25 miles powered by a lead acid battery and sporting electric lights for the first time. (Four years before the first Internal Combustion Engine car by Karl Benz)

1882 In a display of optimism the first small domestic electrical appliances begin to appear, three months before power was available from the first electricity generating station. The electric fan, a two bladed desk fan was invented by Schuyler Skaats Wheeler manufactured by Crocker and Curtis electric motor company and the electric safety iron was invented by New Yorker Henry W. Seely.

1882 The world's first central electricity generating plants or power stations were completed by the Edison Electric Lighting Company. The first to come on stream in April was Holborn Viaduct in London powering 2000 electric lamps. The second, in September, was on on Pearl Street in New York City's financial district, supplying 85 customers. Reciprocating Porter and Allen steam engines provided the motive power (about 900 horsepower) to 27 ton direct-current (DC) dynamos which produced 100 Kilowatts of power at 110 Volts. The overall energy efficiency is estimated at 6%.

1882 Young American engineer William Joseph Hammer testing light bulbs for Edison noted a faint blue glow around the one side of the filament in an evacuated bulb and a blackening of the wire and the bulb at the other side, a phenomenon which was first called Hammer's Phantom Shadow. In an attempt to keep the inside of the electric lamps free of soot he placed a metal plate inside the evacuated bulb and connected a wire to it. He noted the unidirectional or "one-way" current flow from the incandescent filament across the vacuum to the metal plate but he was unable to explain it or realise its significance at the time. It was in fact due to the thermionic emission of electrons (not discovered until 1897 by J.J Thomson) from the hot electrode of the filament, flowing to the cold electrode of the plate creating in effect a vacuum diode or valve. In 1884 Edison was awarded a patent for a device using this effect to monitor variations in the output from electrical generators. The indicator proved ineffective however Hammer's discovery of thermionics was henceforth known as the Edison effect. The Edison effect is the basis of all the vacuum tube devices and thus the foundation of the electronics industry in the early 20th century. The first practical vacuum tube diode was patented by Fleming in 1904.

1882 English engineer John Hopkinson patented the three-wire, three phase system for electricity generation and distribution. This system saved over 50 percent of the copper in the conductor.

Hopkinson died at the age of 49 in a mountaineering accident in Switzerland, together with one of his sons and two of his three daughters.

1883 Charles Edgar Fritts an American inventor built the first practical PhotoVoltaic module by coating selenium wafers with an ultra thin, almost transparent layer of gold. The energy conversion efficiency of these early devices was less than 1%. Denounced as a fraud in the USA for "generating power without consuming matter, thus violating the laws of physics" the idea of solar cells was taken up and commercialised by Siemens in Germany.

1883 Irish physicist George Francis Fitzgerald suggests that Maxwell's theory of electromagnetic waves indicates that radio waves can be produced by an oscillating electric current.

1884 Charles Renard uses a Zinc/Chlorine Flow Battery to power his air ship La France with the chlorine being supplied by an on board chemical reactor containing Chromium Trioxide and Hydrochloric Acid.

1884 Swedish chemist Svante August Arrhenius working at the University of Uppsala published his PhD thesis on the Galvanic Conductivity of Electrolytes explaining the process by which some compounds conduct electricity when in solution. He proposed that when a compound like table salt NaCl (sodium chloride) was dissolved in water, it dissociated into positively and negatively charged "ions" (Greek for "the ones that move") Na+ and Cl- whose motions constituted a current. These ions drift freely through the solution but when positive and negative electrodes are introduced into the electrolyte, as in electrolysis, the ions drift towards the electrode of opposite polarity. He defined acids as any substance, which when dissolved in water, tends to increase the amount of H+ hydrogen ions and bases as any substance, which when dissolved in water, tends to increase the amount of OH- hydroxide ions. (These definitions do not cover all possibilities which are now known to exist).

His 1884 thesis was treated with disbelief and was given the lowest passing grade at the time, however he was vindicated with the discovery of the electron by J J Thomson in 1897 and his disparaged thesis won him the Nobel Prize for chemistry in 1903.

In 1896 Arrhenius was the first to describe the "Greenhouse Effect" and its causes.

1884 French chemist Henri Louis Le Chatelier discovered the chemical equivalent of Lenz Law of electromagnetism. It was published in simpler form 4 years later as: "If the conditions of a system, initially at equilibrium, are changed, the equilibrium will shift in such a direction as to tend to restore the original conditions". The conditions refer to concentration, temperature and pressure. Le Chatelier's Principle allows you to predict which way the equilibrium will move when you change the reaction conditions, and helps provide ways to increase the yield in a chemical reaction.

1884 German engineering student Paul Gottlieb Nipkow patents an electromechanical image scanning system the basis for television raster scanning. The system was made possible by use of the photoconductive properties of the element selenium recently discovered by Fritts. Previous attempts at transmitting images such as Redmond's had used one channel, or pair of wires, to transmit each picture element. Nipkow's design needed only one pair of wires for transmitting the image. He used a rotating disk with holes, through which the scene could be observed, arranged circumferentially around the disc in a spiral between the centre and the edge. Light passing through the holes as the disk rotated, impinged on a selenium photocell, generating an electrical signal proportional to the brightness of the scene which could be transmitted down wires to a receiver. As the disk rotated it produced a rectangular scanning pattern or raster which scanned the scene. The number of scanned lines was equal to the number of holes and each rotation of the disk produced a television frame. A similar Nipkow disc, synchronised with the transmitter disc, was used in the receiver and the received electrical signal was used to to vary the brightness of a light source illuminating a projection screen. The light passing through the rotating disk formed a raster on the projection screen allowing an image to be built up. Like all television systems, it depended on the principle of "persistence of vision" and rapid scanning was needed to ensure that it worked. This was the first example of transmitting moving images electrically down a wire however it is not clear whether Nipkow actually built a working system. The signals from the selenium were very low and needed amplification for a practical system and it was not until 1907 that De Forest's audion made this possible.

1885 German physicist Eugen Goldstein using a cathode ray tube with a perforated cathode discovered rays of positively charged particles emerging from holes on the sides of the cathode and moving in the opposite direction of cathode rays. He called these rays Canal rays. The particles were later determined by Wien to be protons with a mass almost 2000 times the mass of an electron.

1885 Italian physicist Galileo Ferraris discovered the rotating magnetic field that he applied to the first 4 pole induction motor. He did not patent his invention but offered it freely to "the service of mankind"

1885 Russian Nikolai Benardos and Polish Stanislav Olszewski were granted a patent for an electric arc welder with a carbon electrode. They are considered the inventors of modern welding apparatus although electric arc welding was first proposed by Lindsay fifty years earlier in 1835.

1885 Engineers from the Ganz factory in Hungary, Ottó Titusz Bláthy, Miksa Déri and Károly Zipernowsky demonstrated at the National Exhibition in Budapest, a high voltage alternating current distribution system using toroidal transformers which they also designed. The entire exhibition was illuminated by 1,067 X 100 Volt incandescent lamps supplied by 75 transformers taking their power from a 1,350 Volt 70 Hz distribution system.

In modern day power transformers the windings are usually wound around a laminated iron (Silicon steel) core (either directly or on a former). The Ganz transformers at the time provided a breakthrough in efficiency because of their unique construction which improved the transformer's magnetic circuit. The primary and secondary windings were first wound together in the shape of an annular ring and this formed the core of a toroid. The magnetic circuit was made by toroidally winding thousands of turns of iron wire around the copper windings, completely encasing them in magnetic material which almost filled the inner space of the ring.

Bláthy also patented the first alternating-current kilowatt-hour meter in 1889.

1885 German mechanical engineer, Karl Friedrich Benz designed and built the world's first practical automobile to be powered by an internal combustion engine. It was a "three wheeler", powered by a water cooled 958cc, 0.75hp four stroke engine based on Nicolaus Otto's patent with electric ignition and differential gears. He was granted a patent for the gasoline fuelled "motor carriage" the following year and built his first four wheeled car in 1891. His invention marked the start of the slow demise of the battery driven car.

1886 After Bláthy's demonstrations of alternating current power distribution the previous year, New Yorker, William Stanley Jr in the USA patented the "Induction Coil", invented by Michael Faraday in 1831, what we would now call a transformer. This opened the door to the widespread use of AC power for domestic applications. Battery power, once the only source of electricity in the home, now had a serious competitor.

1886 Carl Gassner of Mainz patented the carbon-zinc dry cell which made batteries the convenient power source they are today. It used the basic Leclanché (1868) cell chemistry with zinc as its primary ingredient with the chemicals being encased in a sealed zinc container which acted as the negative electrode. A carbon rod immersed in a manganese dioxide/carbon black mixture served as the positive electrode. Initially the electrolyte was ammonium chloride soaked into the separator which was made of paper, but by adding zinc chloride to the electrolyte the wasteful corrosion of zinc when the cell was idle was reduced - adding considerably to the shelf life. A bitumen seal prevented leakage. Although the technology has been refined by over a century of development, the concepts and chemistry are the same as Gassner's first cells.

Previously most wet primary cells could be recharged mechanically by replacing the spent chemicals. The used electrolyte could then be recycled to recover the the basic constituents. The advent of the dry cell marked the beginning of the single use, throwaway cell since it was no longer easy or possible for the user to replace or replenish the active chemicals.

1886 Patent granted to American chemist Charles Martin Hall for the electrolytic process for extracting aluminium from its bauxite ore, aluminium oxide or alumina. His discovery was made in a laboratory he set up at home, using home made Bunsen batteries, shortly after finishing his undergraduate studies. The process was discovered simultaneously by French chemist Paul Heroult and is now called the Hall-Heroult process.

Aluminium is the most abundant metal and the third most abundant element in the earth's crust but, because it is highly chemically reactive, it does not occur in nature as a free metal. Before Hall discovered a practical way of extracting it from its ore, aluminium metal was extremely rare and cost more than gold.

On an industrial scale the process uses enormous amounts of electricity, consequently aluminium extraction plants are normally located close to the sources of cheap hydroelectric power.

1887 Arrhenius publishes the equation named after him showing the exponential relationship between the rate at which a chemical action proceeds and its temperature, the rate doubling with each 10°C rise in temperature.

1887 American inventor Elihu Thomson patents the electric welding (resistance welding) process. The technique used for making battery interconnections.

1887 By 1887 huge strides had been made in the electrical power industry since the invention of the first practical dynamo 20 years earlier.

1887 - 1890 Croatian-born physicist Nikola Tesla filed for numerous US patents on AC distribution systems and polyphase induction motors and generators based on the rotating field principle he discovered in 1882. This enabled inexpensive and unlimited electric power to be brought to the home consumer thus sealing the fate of the DC system and the use of DC in domestic applications.

Contracted for $50,000 by Thomas Edison (a supporter of DC transmission) to improve his DC dynamos Tesla worked night and day to deliver the solutions on time a year later to Edison but Edison refused to pay saying he had been a joking about the contract. Tesla resigned in disgust and went to work for George Westinghouse promoter of AC distribution and Edison's arch rival. Edison with some success, spent the rest of his life trying to undermine Tesla.

For two years after Tesla left, Edison staged a morbid public relations campaign in the notorious current wars to demonstrate that the Westinghouse AC distribution system was dangerous by promoting the AC powered electric chair for carrying out the death penalty and calling such executions "Westinghousing". At the same time he arranged public executions of farm animals which he attended personally in the courtyard of his laboratory using AC power, starting with dogs and escalating to calves then horses.

Edison's system itself was responsible for a number of deaths due to mechanical failure or ignorance as the deceptively similar high voltage wires were installed overhead near to the more familiar low voltage telegraph wires.

In 1915 Reuters and the New york Times carried reports that Tesla and Edison were to share the Nobel Prize for physics. Mystery surrounds what happened next, but no such prize was awarded and it is claimed that Edison, whose fame and wealth were secure, turned down the award to deprive Tesla of a much needed $20,000. Others claim Tesla himself turned it down not wanting to be associated with Edison whom he called "a mere inventor". The Nobel Foundation did not deny that Tesla and Edison had been their first choices.

1887 British engineer, born in Liverpool, with the distinctly un-British name of Sebastian Pietro Innocenzo Adhemar Ziani de Ferranti, (his father was a photographer and his grandfather, Guitarist to the King of Belgians), designed the generation and distribution systems for Deptford Power Station (1887-1890), which at that time was the largest in the world. Power was supplied by four single phase 1000 kW, 10,000 Volts, 85 cycle/sec alternators. Ferranti pioneered the use of Alternating Current for the distribution of electrical power in Europe authoring 176 patents on the alternator, high-tension cables, insulation, circuit breakers, transformers and turbines.

Ferranti also designed the first flexible high voltage cables for power distribution using wax-impregnated paper for insulation, a technique which was used exclusively until synthetic materials became available.

In the same year Ferranti also patented the induction furnace in which materials are heated by eddy currents induced within the material itself, generated by placing the material in the magnetic field of an induction coil.

1887 British physiologist Augustus Waller of St. Mary's Medical School in London published the first human electrocardiogram - recorded by lab technician Thomas Goswell.

1887 Fibreglass invented again by Charles Vernon Boys a physics demonstrator at the London's Royal College of Science who produced glass fibre strands by using the end of an arrow fired from a miniature crossbow to draw strands of molten glass from a heated vessel.

1887 German physicist Heinrich Rudolf Hertz discovered the photoelectric effect, that physical materials emit charged particles (electrons) when they absorb radiant energy. During electromagnetic wave experiments he noticed that a spark would jump more readily between two electrically charged spheres when there surfaces were illuminated by the light from the other spark. Light shining on their surfaces seemed to facilitate the escape of electrons.

The photoelectric effect was not explained until 1905 by Albert Einstein who used quantum theory proposed in 1900 by Max Planck.

1888 Hertz was the first to transmit and receive radio waves. He demonstrated the existence of electromagnetic waves, predicted by Maxwell in 1864 and justified theoretically by him in 1873, by transmitting an electrical disturbance between two unconnected spark gaps situated 1.5 metres apart. He set up a wire loop containing spark gap (the transmitter) through which a large spark was deliberately generated. This caused a small spark to jump across another spark gap (the detector) at the ends of a similar wire loop situated near to but not connected to the transmitting loop. The wire loops were effectively the world's first radio transmitting and receiving antennas.

He showed that radio waves travel in straight lines and can be reflected by a metal sheet.

Hertz died of a brain tumour at the age of 36 without ever seeing the practical applications which resulted from his discoveries. The unit of frequency is named the Hertz in his honour.

Like Hughes who discovered the phenomenon before him, Hertz failed to see the potential of radio for communications. Hertz told one of his pupils " I don't see any useful purpose for this mysterious, invisible electromagnetic energy".

Hertz' (or should we say "Maxwell's") radio waves now form the basis of all broadcast radio and television, radar, satellite navigation, mobile phones and much of the backbone of the world's communications systems. Maxwell provided the theoretical basis for the technology, Hertz showed it was possible but there were many, many worthy contributors whose inventions were needed to make it happen. Each country had its national champions who invented transmitters, receivers, antennas, tuners, detectors, filters, oscillators, amplifiers, transducers, displays, batteries and other components and a variety of coding, modulation, multiplexing, compression, encryption schemes, communications protocols and software. There were however five players associated with the fundamental developments in radio technology whose contrasting fortunes are worth mentioning briefly here namely: Marconi, Fessenden, Armstrong, Watson-Watt and Dippy.

The demand for batteries of course benefited from all of these new developments.

1888 German physicist Wilhelm Ludwig Franz Hallwachs discovers another example of photoelectric emission. (Becquerel's was the first). Following up Hertz' experiments on how light affected the intensity of spark discharges, he noticed that the charge on an insulated, negatively charged plate leaked away slowly but when it was illuminated with ultraviolet light the charge leaked away very quickly. On the other hand a positively charged plate was unaffected by the light. This phenomenon, now known as the Hallwachs effect, was later explained to be due to the emission of electrons from certain metallic substances when exposed to light. It is the basis of the modern photocell. Note that this is different from the photovoltaic effect in solar cells.

1888 Spanish naval officer Isaac Peral built the first electrically powered submarine.

Later the same year the French launched Gymnôte, a 60 foot submarine designed by Gustave Zede. It was driven by a 55 horse power electric motor, originally powered by 564 Lalande Chaperon alkaline cells by Coumelin, Desmazures et Baillache with a total capacity of 400 Amphours weighing 11 tons and delivering a maximum current of 166 Amps. These batteries were replaced in 1891 by 204 Laurent-Cely Lead acid cells, which were in turn replaced in 1897. Although the batteries were rechargeable, they could not be charged at sea.

An electric submarine was also built by Polish inventor Stefan Drzewiecki for the Russian Tzar in 1884.

1888 Austrian botanist Friedrich Reinitzer investigating the behaviour of cholesterol in plants observed cholesteryl benzoate changing into its liquid crystal state, nine years before the invention of the CRT. For nearly a hundred years afterwards liquid crystals remained little more than a chemical curiosity. See Dreyer (1950) and Heilmeyer(1968)

1889 Russian engineer Michail Osipovich Dolivo von Dobrovolski working for AEG in Germany made the first squirrel cage induction motor.

1889 Walther Hermann Nernst a German physical chemist applied the principles of thermodynamics to the chemical reactions proceeding in a battery. He formulated an equation (now called the Nernst Equation) for calculating the cell voltage taking into account the electrode potentials, the temperature and the concentrations of the active chemicals. It applies to the equilibrium position i.e. no current. This is a special case of the more general Gibbs free energy relationship and is one of the basic formulas used by cell designers to characterise the performance of the cell.

He also showed that in a reversible system the electrical work done is equal to the change in free energy. Also known as the enthalpy.

Nernst stated the Third Law of Thermodynamics that it is impossible to cool a body to absolute zero, when it would have zero entropy, by any finite process. In a closed system undergoing change, entropy is a measure of the amount of energy unavailable for useful work. At absolute zero, when all molecular motion ceases and order is assumed to be complete, entropy is zero.

1889 America's first alternating current (AC) hydroelectric power generating station was put into service at Willamette Falls, Oregon. Using Westinghouse generators it was also America's first AC transmission system providing single phase power at 4000 Volts which was transmitted to Portland 14 miles away where it was stepped down to 50 Volts for distribution and used to power the street lights.

1890 Dundee born engineer James Alfred Ewing discovers the phenomenon of hysteresis which he named after the Greek "hysteros" meaning "later". He observed that, when a permeable material like soft iron is magnetised by being subjected to an external magnetic field, the induced magnetisation tends to lag behind the magnetising force. If a field is applied to an initially unmagnetised sample and is then removed, the sample retains a residual magnetisation becoming a permanent magnet. He speculated that individual molecules act as magnets, resisting changes in magnetising potential and described the characteristic curve of the magnetic induction B versus the magnetic field H which caused it, calling it a hysteresis loop (diagram). Also known as the BH loop, it was later shown by Steinmetz that the area of the hysteresis loop is proportional to the energy expended in taking the system through a complete magnetisation - demagnetisation cycle. This wasted energy appears as heat and represents a considerable energy loss in alternating-current machines which are subject to cyclic magnetic fields. On the other hand, hysteresis is useful for creating permanent magnets or temporary magnetic memory, once the main method of providing computer Random Access Memory (RAM).

The hysteresis loop is the signature of a magnet. A slender loop indicates a good temporary magnet which has low hysteresis losses and responds readily to a small magnetic field. Temporary magnets (also known as soft magnets) are needed in magnetic circuits subject to cyclic field such as those found in motors, generators, transformers and inductors. A fat hysteresis loop indicates a permanent magnet, or hard magnet, which will remain magnetized after the application and withdrawal of a large magnetic field.

The term "hysteresis" is now used to describe any system in whose response depends not only on its current state, but also upon its past history.

1891 German born, American mathematician and engineer Charles Proteus (Karl August) Steinmetz developed an empirical law for determining the magnitude of the losses due to the recently discovered phenomenon of magnetic hysteresis which he published in the magazine, "The Electrical Engineer".

The Hysteresis law for the loss of energy per magnetization cycle per unit volume "W" is given by Steinmetz's equation as

where B_max is the maximum flux density, η is the hysteresis coefficient or (a constant depending on the molecular structure and content of the material) and x is the Steinmetz exponent between 1.5 and 2.3, typically 1.6

Steinmetz also provided data on the magnetic characteristics of all magnetic materials then in current use.

As a rule of thumb, when the magnetic flux induced by the alternating current doubles, the hysteresis loss triples. The ability to predict the hysteresis losses for different materials and shapes enabled the design of more efficient machines, a process which had previously been trial and error.

In 1893 Steinmetz developed the phasor method using complex or imaginary number notation for representing the the varying currents and voltages in AC circuits. This simple and practical method revolutionised the analysis of AC circuits.

Called the Wizard of Schenectady where he worked for General Electric, Steinmetz also carried out research on lightning phenomena. He was a prolific inventor with over 200 patents to his name including an electric car, the 1917 Dey electric roadster, for which he designed a compact double-rotor motor which was an integral part of the rear axle avoiding the need for a differential.

Steinmetz was physically handicapped with a deformed left leg, humped back, and diminutive stature, only four foot three inches (1.3M) tall, but he was compensated by a brilliant mind, congenial personality and infectious vitality. Raised in poverty, Steinmetz was a lifelong socialist whose early political activities brought him into conflict with the German authorities resulting in his flight from Germany. Throughout his life he applied his considerable energies to helping others.

1891 Another patent for the three-phase electric power generation and transmission system, this one granted to Jonas Wenström a Swedish engineer. His patent was disputed for many years by other claimants, including Hopkinson who patented the principle in 1882. It was finally confirmed in 1959, sixty eight years after Wenström died.

1891 American electrial engineer Harry Ward Leonard introduced the motor speed control system which bears his name. For almost a century, until the advent of thyristor controllers, it was the only practical way of providing a variable speed drive system from the fixed frequency mains electricty supply.

1891 Hertz, with his Hungarian student Philipp Eduard Anton von Lenard, discovered that cathode rays could penetrate a thin aluminium plate. Because gas could not pass through the foil they surmised that the cathode ray was a wave, publishing their results in 1894. In 1897 J.J. Thomson showed that cathode rays were streams of particles which he called corpuscles and which we now call electrons.

Lenard was awarded the Nobel Prize for Physics in 1905 for his work on cathode rays. He was a strong proponent of the German "Master Race" and became Adolf Hitler's advisor and Chief of "Deutsche Physik" or "Aryan Physics". He claimed that so called "English physics" had stolen their ideas from Germany and denounced Einstein's theory of relativity as a deliberately misleading Jewish fraud perpetrated by "Jewish physics". He was expelled from his post at Heidelberg University by the Allied occupation forces in 1945.

1892 British born American chemist Edward Weston invented and patented the saturated cadmium cell. Known as the Weston Standard Cell, it was adopted as the International Standard for electromotive force (EMF) in 1911 and was used as a calibration standard by the US National Bureau of Standards for almost a century. It had the advantages of being less temperature sensitive than the previous standard, the Latimer Clark Standard Cell which it replaced and of producing a voltage of 1.0183 Volt, conveniently near to one Volt. Similar to Clark's cell it used a Cadmium anode rather than Zinc.

He had revolutionised the electroplating industry in 1875 by replacing the batteries used to provide the current used in the plating process with dynamos which he designed and made himself and in 1886 he developed a practical precision, direct reading, portable instrument to accurately measure electrical current, a device which became the basis for the moving coil voltmeter, ammeter and watt meter.

1892 The Hayes patent paved the way for telephone signalling and speech to be powered from a single large central 24 Volt lead acid batteries mounted in central telephone exchanges, eliminating the need for magnetos and Leclanché cells installed in every subscriber's premises. The system is still in use today.

1892 Eccentric Kentucky melon farmer Nathan B. Stubblefield "demonstrated" wireless telephony using a ground battery or earth battery (first proposed by Bain in 1841), for transmitting signals through the ground. Extravagant claims were made for the applications of the ground battery, from telephony and broadcasting to power generation, but they were never substantiated and Stubblefield, claiming he was swindled, died of starvation, an impoverished recluse. He is honoured in his hometown of Murray, Kentucky as "The Real Father of Radio".

1892 Dutch physicist Hendrik Antoon Lorentz formulates Lorentz Law, a fundamental equation in electrodynamics which gives the force F on a charged particle in an electromagnetic field as the sum of the electrical and magnetic components as follows:

Where q is the charge on the particle, v is its velocity, E is the electric field and B is the magnetic field.

Lorentz developed a mathematical theory of the electron before their existence was proven for which he received the Nobel Prize in 1902

1893 Two German schoolmasters Johann Phillip Ludwig (Julius) Elster and Hans Friedrich Geitel discovered the sensitive photoelectric effect of alkaline metals such as sodium or potassium in vacuum tube at visible light spectrum. They later design the first practical photoelectric cell or "electric eye" which provides a voltage output which varies in relation to the intensity of light impinging upon it. They decline to patent their invention. The photoelectric effect is the basis of all electronic image tubes.

1893 Contract to supply hydroelectric generators to harness the power of Niagara Falls using Tesla's AC system awarded to Westinghouse, signalling the beginning of the end for DC generation and transmission, the end of the Current Wars and a triumph for Tesla. Rival Edison had lined up influential backers including J. P. Morgan, Lord Rothschild, John Jacob Astor IV, W. K. Vanderbilt and initially Lord Kelvin, a proponent of direct current, who headed an international commission to choose the system. After seeing Tesla's AC system which was used to light the 1893 World's Columbian Exposition at Chicago, Kelvin was converted to a be supporter of the AC system.

The system was completed in 1895 with three enormous 5,000 horsepower generators supplying 2,200 Volts for local consumption, stepped up to 11,000 Volts for transmission to Buffalo 22 miles away. The capacity was later increased to 50,000 horsepower with 10 generators and the transmission Voltage increased to 22,000 Volts for longer distance transmission.

1894 British engineer Charles Algernon Parsons had produced his first steam turbine in 1885 but had failed to generate any commercial interest in it. To publicise his invention, in 1894 he took out a patent on the turbine and commissioned a 100 foot long steel boat, the Turbinia, to demonstrate its capability. Initially he did not achieve the desired speed through the water as its propellers, rotating at 18,000 rpm, suffered from the previously unheard of problem of cavitation and churned up the water as bubbles formed behind the blades due to sudden pressure reduction. However by slowing down the turbine and modifying the propellers he was able to achieve a speed of 34.5 knots. Still his target customer the Admiralty were unimpressed. According to Parson's biographer Ken Smith, Parsons dictum was "If you believe in a principle, never damage it with a poor impression. You must go all the way". His opportunity came at the 1897 Spithead Naval Review of 160 of the navy's ships, arranged to show off the might of the Royal Navy to Queen Victoria and invited foreign dignitaries on the sixtieth anniversary of the queen's accession to the throne. The navy's best boats were capable of no more than 30 knots and the Turbinia astonished the gathered crowd by steaming up and down the navy's lines leaving their fastest boats in her wake. The steam turbine's future was assured. Today 86% of the world's electricity is generated using steam turbines.

1895 German physicist Wilhelm Conrad Röntgen experimenting with a Crookes tube accidentally discovered X-rays while investigating the glow from the cathode rays and gave his preliminary report "Uber eine neue Art von Strahlen" to the president of the Wurzburg Physical-Medical Society, accompanied by experimental radiographs and by the image of his wife's hand. Within three years, every major medical institution in the world was using X-rays. Röntgen, who won the first Nobel prize in physics in 1901, declined to seek patents or proprietary claims on the use of X-rays. X-ray technology is now widely used in materials science. See Bragg (1912)

1895 French physicist Pierre Curie discovered that the magnetic coefficients of attraction of paramagnetic bodies vary in inverse proportion to the absolute temperature -- Curie's Law. He showed that ferromagnetic materials exhibit a characteristic temperature, now called the Curie point or Curie temperature, above which they lose all their magnetic properties. He also showed that there is no temperature effect for diamagnetism.

1896 Inspired by Hertz, 22 year old Italian Marchese Guglielmo Marconi, son of the Irish-born heiress to the Jameson whiskey fortune, was granted his first patent (in England) for radio telegraphy using Hertzian waves. This was the first application of radio waves and he was the first to show that radio communications were possible. His system however was the radio equivalent of Morse's telegraph, switching the radio wave on and off in "dots and dashes", and it did not carry voice signals. It was Fessenden who first carried voices over the radio waves ten years later. Marconi was a great promoter, he developed transmitters, receivers and antennas and his telegraph systems were soon in use throughout the world, spanning the Atlantic in 1901, and earning him fame and fortune. He was awarded the Nobel prize for physics in 1909.

1896 American engineer William W. Jacques developed a carbon battery producing electricity directly from coal. 100 cells with carbon electrodes and alkaline electrolyte were placed on top of a coal fired furnace that kept the electrolyte temperature between 400-500 °C and air was injected into the electrolyte to react, he thought, with the carbon electrodes. The output was measured as 16 Amps at 90 Volts. Initially, Jacques claimed an 82 percent efficiency for his battery, but he had failed to account for the heat energy used in the furnace and the energy used to drive an air pump. The real efficiency was a meager 8 percent. Further research demonstrated that the current generated by his apparatus was not obtained through electrochemical action, but rather through thermoelectric action.

1896 Antoine Henri Becquerel discovered radioactivity when Uranium crystals wrapped in paper and left in a drawer with photographic plates created an image of the crystals on the plates. Radioactivity is the spontaneous breakdown of unstable atomic nuclei resulting in the emission of radiation which may be alpha particles (Helium nuclei), beta particles (electrons), nucleons (neutrons or protons), or gamma rays (high energy electromagnetic radiation). At the time however the nature of these mysterious rays was not known and it was several years before Rutherford and others were able to identify the content of the radiation.

Radioactivity can come from the decay of naturally occurring radioisotopes. Nuclear batteries are designed to make use of the radiated energy of certain radioactive isotopes by converting it into electrical energy.

Becquerel came from a distinguished family of scholars and scientists. His father, Alexandre-Edmond Becquerel, was a Professor of Applied Physics, discovered the photovoltaic effect and had done research on solar radiation and on phosphorescence, while his grandfather, Antoine César Becquerel, had been a Fellow of the Royal Society and invented a non polarising battery and an electrolytic method for extracting metals from their ores.

1896 In the USA, the flashlight or torch was invented by David Misell. The original versions were designed to attach to a tie or scarf and were sold by a Russian immigrant, Conrad Hubert in his novelty shop where Misell went to work. Although portable battery powered lamps had been in use in the UK since 1881 where they were patented by Burr and Scott, the first flashlight as we know it today introduced by Hubert in 1898. It was designed by Misell and was powered by a "D" cell which, with the light bulb and a rough brass reflector, was contained in a paper tube. Hubert went on to found Ever Ready and patents for subsequent flashlights although designed by Misell were awarded to Hubert.

The invention of the tungsten filament lamp by Coolidge in 1910 greatly improved the performance of the torch which in turn created a growing market for batteries, popularising the "D" cell format we still use today.

1896 H. J. Dowsing patented the electric starter which he fitted to a modified Benz motor car purchased from maker Walter Arnold who made them under licence as the Arnold Sociable in East Peckham, Kent. Dowsing's starter consisted of a dynamotor, coupled to a flywheel, which acted as a dynamo to charge the battery and as a motor when needed to start the engine, an idea recently rediscovered as the integrated starter alternator (ISA). The first production electric self-starter was produced by Dechamps in Belgium in 1902.

1897 British physicist Joseph John (J J) Thomson working at the Cavendish Laboratory in Cambridge investigating the affect of magnetic fields on cathode rays in a Crookes tube discovered the electron and calculated the ratio between its charge and its mass, the e/m ratio. He determined that they were identical particles no matter what metal had emitted them and that they were the universal carriers of electricity and a basic constituent of matter. He also calculated the velocity of the electron in the cathode ray to be 1/10 of the speed of light. J.J. Thomson was awarded the Nobel prize in 1906 for his studies on the conduction of electricity through gases and for the discovery of the electron and his pioneering work on the structure of the atom.

At the time there was great rivalry between German researchers who believed cathode rays to be waves and their British counterparts who believed them to be particles. In one of the greatest ironies of modern physics J.J. Thomson was awarded the Nobel Prize for showing that the electron is a particle, while his son, George Paget Thomson later received the Nobel prize for proving that the electron was in fact a wave.

Thomson died in 1940 and in his lifetime he never drove a car or travelled in an aeroplane. He had a passion for nature and said that if he had to live his life over again he would be a botanist.

Ever since Faraday published his work on the magnitude of the weights of the products of electrolysis in 1833, experimenters had postulated the idea that electric current was carried by corpuscles or particles but none had been able to isolate or describe such particles. By the late 1890's however, several other investigators working contemporaneously with Thomson had identified the charged particle we now call the electron and calculated the e/m ratio just as Thomson did in April1897. These included Pieter Zeeman at the University of Leiden who in 1896 observed the spreading of spectral lines caused by the influence of a magnetic field and concluded that the light waves were produced by the movement of ions. From the experiment he was able to calculate the e/m ratio. At the same time, each working independently with cathode rays, Emil Weichert at the University of Köningsburg, Walter Kaufmann at the University of Berlin and Philipp Lenard an assistant of Heinrich Hertz carrying on Hertz' experiments after his death, all published similar results for the value of the e/m ratio early in 1897. It was Thomson however who identified the electron as a sub atomic particle, while the others were hampered by trying to reconcile the evidence of a particle with the notion of the aether.

History is kind to the winners of Nobel prizes. Once conferred, the other participants in the race are forgotten.

1897 The first oscilloscope using a cathode ray tube (CRT) scanning device was invented by the German scientist Karl Ferdinand Braun. He made many contributions to radio technology including antennas and detectors. He was awarded the Nobel prize with Marconi in 1909 for this work. During the first World War he was interned by the US government as an enemy alien and died before the war ended.

1897 Regenerative braking first used on a car to recharge the battery by M. A. Darracq in Paris

1897 German researcher W. Peukert discovered that the faster a battery is discharged the lower its available capacity, a phenomenon for which he developed the empirical law C = IⁿT known as the Puekert Equation where "C" is the theoretical capacity of the battery expressed in amp hours, "I" is the current, "T" is time, and "n" is the Peukert Number, a constant for the given battery. A similar phenomenon occurs when a battery is charged. See also charging times for an explanation and a beer analogy.

1898 Danish telephone engineer Valdemar Poulsen patented the Telegraphone, the first magnetic recording and playback apparatus. It used a magnetised wire as the recording medium.

1898 The Proton discovered by German physicist Wilhelm Wien. Using an apparatus designed by Goldstein which generated canal rays of positively charged particles he determined that canal rays were streams of protons with mass equal to the mass of a Hydrogen atom. Rutherford later coined the word proton in 1919.

Wien also discovered the inverse relationship between the wavelength of the peak of the emission of a black body and its temperature now called Wien's Law. He was awarded the Nobel Prize in 1911 for his work on Black Body Radiation.

1898 British physicist Oliver Joseph Lodge patented the principle of tuned circuits which he called "syntonic tuning" for generating and selecting particular radio frequencies. This is the basis of selecting a single desired radio station from all those which are transmitting by tuning the receiver to the transmitter. Not only was this more efficient, it was fundamental to the orderly use of the radio spectrum and the establishment of practical radio communications systems which did not interfere with eachother.

1898 Pierre and Marie Sklodowska Curie discovered Radium named from the Latin "radius" meaning "ray" and Polonium which Marie named after her native Poland. With very limited resources, during the course of four years, the Curies refined 8 tonnes of waste pitchblende to produce 1 gram (0.04 ounces)of pure Radium Chloride. (It was not until 1911 that she was able to isolate pure Radium). Radium is over one million times more radioactive than the same mass of Uranium and one gram of Radium releases 4000 kilo joules (1.11 KWh) of energy per year. In 1900 they showed that beta rays and cathode rays are identical. Unaware at the time of the dangers of radiation in 1903 they both began to show signs of radiation sickness. Marie shared the 1903 Nobel Prize for Physics with her husband Pierre and Henri Becquerel for the investigation of radioactivity, a phenomenon which she named. In 1906 Pierre was unfortunately killed when he was run over by a horse drawn cart. Marie continued their investigations and in 1911 was awarded a second Nobel Prize, this time for Chemistry for her discovery of two new elements.

Despite her achievements and her two Nobel prizes, she was rejected by the French Academy of Sciences when seat for a physicist became vacant. During her life she worked tirelessly for humanitarian causes and the use of X-rays and radioactivity in medical research, refusing to patent any of her ideas. She died of leukaemia caused by prolonged exposure to radioactivity. Her laboratory notebooks are still considered too radioactive to handle and photographic films, when placed between the pages, show the images of Madame Curie's radioactive fingerprints when developed. A year after her death, her daughter Irene won the family's third Nobel Prize.

1899 Charles H. Duell Commissioner in the US Office of Patents announced "Everything that can be invented has been invented"

1899 Working at McGill University in Montreal on Becquerel's mysterious rays, New Zealand physicist Ernest Rutherford, assisted by English chemist Frederick Soddy, discovered two kinds of "rays" emanating from the Uranium, one of which he called the alpha rays, could be absorbed by a sheet of writing paper. The other which he called beta rays was one hundred times more penetrating but could be stopped by a thin sheet of aluminium. Meanwhile French physicist Paul Ulrich Villard found that Radium emitted some far more penetrating radiation, which he christened gamma rays. These rays could penetrate several feet of concrete.

It was still some time before the properties of all these different rays could be determined.

1899 The world land speed record of 68 mph was set by a Belgian built electric car, the "Jamais Contente", designed and driven by Camille Jénatzy. The first to exceed 100 kph, his cigar shaped car was powered by two 80 cell Fulmen Lead acid batteries supplying two twelve volt, 25 kilowatt motors, integral with the rear axle, driving the rear wheels directly.

Jénatzy, known as the Red Devil because of his red beard, was a famous racing driver at the time when racing was very dangerous, however his life was ended at his country estate rather than on the race track when, hosting a shooting party, he sneaked into the woods to imitate a roaring bear and was shot by one of his friends.

1899 Young German engineer Ferdinand Porsche, working at the Jacob Lohner Company, built the first Hybrid Electric Vehicle (HEV), a series hybrid, optimised for simplicity and efficiency. It used a petrol engine rotating at optimum, constant speed to drive a dynamo which charged a bank of batteries which in turn provided power to hub mounted electric motors in the front wheels. 300 Lohner Porsches were produced.

1900 Thomas Alva Edison in the USA also patents a rechargeable alkaline cell, the Nickel Iron (NiFe) battery. Another one of Edison's 1093 patents.

Nickel Iron batteries were very robust, designed for powering electric vehicles, but with the rise of the internal combustion engine their main applications became railway traction, fork lift trucks and utilities.

1900 Sales of internal combustion engined cars overtake sales of electric cars for the first time.

1900 German physicist Max Planck announced the basis of what is now known as quantum theory, that the energy emitted by a radiating body could only take on discrete values or quanta. Planck's concept of energy quanta conflicted fundamentally with all past classical physics theory and eventually gave birth to the particle theory of light as later explained by Albert Einstein. Although its importance was not recognised at the time, quantum theory created a revolution in physics. Planck was driven to introduce it strictly by the force of his logic; he was, as one historian put it, a reluctant revolutionary.

The energy E in a quantum of light, now called a photon, or resonator of frequency ν is hν where h is a universal constant equal to 6.63 X 10^-34 Joule seconds (Js), now called Planck's constant.

Planck's personal life was a tragic one. His first wife died early leaving Planck with two sons and twin daughters. The elder son was killed in action in 1916 in the First World War. Both of his daughters died in childbirth. World War II brought further tragedy. Planck's house in Berlin containing his technical papers was completely destroyed by bombs in 1944. Far worse his younger son died while being tortured by the Gestapo after being implicated in the attempt made on Hitler's life in 1944. Planck died in 1947 at the age of 88.

1900 German physicist Paul Karl Ludwig Drude developed a model to explain electrical conduction based on the kinetic theory of electrons moving through a solid.

1900 Belgian car maker, Pieper, introduced a 3½ horsepower "voiturette" another variant of the hybrid electric vehicle (HEV). An electric motor/dynamo was mounted in line with a small petrol engine and acted as a generator during normal driving, recharging the batteries. For hill climbing the motive power was augmented by battery power as the electric motor was switched to supplement the power of the engine.

Later versions used higher capacity batteries (28 Tudor batteries in series) and a 24 horsepower engine connected to a higher power electrical drive via a magnetic clutch. The clutch mechanism allowed energy to be recovered by regenerative braking as well as the use of the higher power electric motor to drive the vehicle on its own.

1900 Irish born American John P. Holland launched his first submarine the Holland I in 1878. A crude design, carrying a crew of one, it was powered by a petrol engine and ran on compressed air when submerged. Holland was a sympathiser of the Fenian Brotherhood, an Irish revolutionary secret society, forefathers of the IRA, founded in the United States. He designed the Fenian Ram, a three man submarine which was launched in 1881, for attacking British shipping. Finding the Fenians unreliable customers he made several unsuccessful attempts to sell his submarines to the US government, eventually launching his sixth submarine the Holland VI in 1898. It was a dual propulsion submarine the which used a 45 h.p. Otto petrol engine for propulsion and battery charging while on the surface and a 110 Volt electric motor powered by 60 Lead Acid cells with a capacity of 1500 ampere hours for propulsion when submerged. This time his demonstration was successful and the submarine was purchased by the US government. It was commissioned in 1900 and renamed the USS Holland, also known as the SS1, becoming the US Navy's first submarine. Although it carried a crew of only five plus an officer, the Holland VI was a major breakthrough in submarine design. For the first time, all the major components were present in one vessel - dual propulsion systems, a fixed longitudinal centre of gravity, separate main and auxiliary ballast systems, a hydrodynamically advanced shape, and a modern weapons system. The configuration and design principles used in the Holland VI remained the model for all submarines for almost 50 years.

1901 Patent granted to Michaelowski in Russia for the rechargeable Nickel Zinc battery.

1902 The Mercury Arc Rectifier invented by American engineer Peter Cooper Hewitt. A spin off from developments of the mercury arc lamp it was capable of rectifying high currents and found use in electric traction applications which used DC motors.

1902 Twenty years after the introduction of electricity supply in the USA only 3% of the population were served by electricity.

1903 The invention Electrocardiograph by Indonesian born Dutchman Willem Einthoven was announced after a long gestation period. Building on Waller's work of 1887 (and the contributions of many others following in the footsteps of Galvani) it used a sensitive "string galvanometer" of Einthoven's own design to pick up small electrical currents from the patient's torso and limbs. (Galvani's theories about Animal electricity vindicated?)

Einthoven is now credited with the design of the electrocardiograph for which he received the Nobel Prize in 1924.

1903 Following on from their work on radiation, Soddy and Rutherford proposed that the phenomenon of radioactivity was due to the spontaneous atomic disintegration of unstable heavy elements into new, lighter elements, an idea which, like many new scientific theories, was treated with derision at the time.

Soddy was a chemist and Rutherford a passionate physicist who believed that chemistry was an inferior science to physics. Ironically it was Rutherford rather than Soddy who was honoured in 1908 with the Nobel Prize for chemistry for the discovery of radioactive transformation. Afterwards Rutherford liked to joke that his own transformation into a chemist had been instantaneous. Soddy resented the the fact that his contribution had not been recognised. He was however eventually awarded a Nobel prize in 1921 for his work on isotopes but that did little to mitigate his earlier slight.

1903 British Patent awarded to German Albert Parker Hanson, living in London, for flexible printed wiring circuits intended for use in telephone exchanges. Based on flat parallel copper conducting strips bonded to paraffin waxed paper. The design used a double layer construction with the copper strips in alternate layers perpendicular to the layer below forming a rectangular grid. Interconnections were crimped through holes in the paper. As well as through hole connections, Hanson's patent also described double-sided and multilayer boards.

1903 The Compagnie Parisienne des Voitures Electriques produced the Krieger front wheel drive hybrid electric vehicle (HEV) with power steering. A petrol engine supplements the battery pack.

1903 Russian botanist Mikhail Semenovich Tswett invented the technique of chromatography (Latin "colour writing") which he demonstrated by passing extracts of plant tissue through a chalk column to separate pigments by differential adsorption. It was derided at the time but the principle is now used universally for separating and identifying different chemical compounds from samples.

1903 The teleprinter machine (a.k.a. teletypewriter, teletype or TTY) invented by New Zealand sheep farmer Donald Murray. It could punch or read five digit Baudot coded paper tapes (Murray used his own modified version) and at the same time print out the message on a sheet of paper. It de-skilled the telegraph operator's job, since they no longer needed to know Morse code, and at the same time greatly speeding data communications. The teleprinter remained in widespread use until the 1970's when electronic data processing and computer networking replaced many of its functions.

1904 British physicist John Ambrose Fleming invented the first practical diode or rectifier. Although first used in radio applications it became an important device for deriving direct current from the alternating current AC electricity distribution system, revitalising opportunities for DC powered devices, and indirectly, batteries. Fleming's invention of the thermionic valve (tube) could be said to be the beginning of modern electronics. Fleming also invented the potentiometer.

1904 German engineer Christian Hülsmeyer invented and patented the first practical radar for detecting ships at sea which he called the Telemobiloscope. It consisted of a spark gap transmitter operating in the frequency range of 650 MHz, whose emissions were focused by a parabolic antenna located on the mast of the ship. The receiving antenna picked up the reflected signals and when a ship was detected a bell was automatically rung. Using continuous wave transmissions, it was unable to measure distances. its range was limited to about one mile and at the time neither government nor private companies were interested in it.

1904 Patent granted to Harvey Hubbell in the USA for the "separable attachment-plug", the first 110 Volt AC mains plug and socket. Still in use today.

It is surprising that we had electric lights and motors, three phase power generation and distribution, cathode ray tubes, x-ray and electrocardiograph machines, alpha, beta and gamma rays, and batteries were over one hundred years old, all before the humble plug and socket were invented.

1904 Taking steam from the local volcanic hydrothermal springs, Prince Piero Ginori Conti tested the first geothermal power generator at the Larderello in Italy, using it to power four light bulbs. Seven years later, the world’s first geothermal power plant was built on the same site.

1905 Annus Mirabilis - Einstein's miraculous year. In those twelve months, 25 year old patent clerk Albert Einstein, shook the foundations of classical physics with five great papers that established him as the world's leading physicist.

Einstein once said "The hardest thing in this world to understand are income taxes".

1905 The experimental findings of the German physical chemist Julius Tafel on the relationship between the internal potentials in a battery and the current flowing were summarised in Tafel's equation. It is a special case of the more theoretical Butler-Volmer equation (1930) which quantifies the electrochemical reactions in a battery.

1905 H Piper in the USA patents the hybrid electric vehicle (HEV), a concept introduced in 1899 by Porsche in Germany and in Belgium by Pieper in 1900 and later demonstrated by Krieger in 1903 in France. A top speed of 25 mph was claimed.

1905 French physicist Paul Langévin finally explained the cause of magnetism. He suggested that the alignment of molecular moments of the molecules in a paramagnetic substance were caused by an externally applied magnetic field and that the influence of the magnetic field on the alignment becomes progressively stronger with increasing temperature due to the thermal motion of the molecules. He also suggested that the magnetic moments of the molecule, the magnetic properties of a substance, are determined by the valence electrons. This notion subsequently influenced Niels Bohr in the construction of his classic model of the structure of the atom.

Langévin also pioneered the use of high intensity ultrasound for use in sonar applications.

1906 Canadian inventor and eccentric genius Reginald Aubrey Fessenden was the first to transmit and receive voices over radio waves, inventing the so called wireless which made broadcast radio possible. While Marconi's invention was equivalent to Morse's, Fessenden's invention was equivalent to Bell's. Bell superimposed a voice signal onto a DC current whereas Fessenden superimposed the voice signal onto an radio wave (a high frequency AC signal known as the carrier wave) varying the amplitude of the radio wave in a process known as amplitude modulation (AM radio).

He offered the rights to the patents which covered his radio broadcasting system to AT&T but they found it was was "admirably adapted to the transmission of news, music, etc." simultaneously to multiple locations, but they decided that it was not yet refined enough for commercial telephone service.

Fessenden was a prolific inventor, with over 500 patents relating to radio and sonar to his name including 5 for the heterodyne principle which made Armstrong rich and famous, but he never got the recognition he deserved. He was neither a good businessman nor an accomplished promoter and lost control of his patents and the possible wealth that flowed from them, dying a bitter and forgotten man.

1906 Patent awarded to American engineer Greenleaf Whittier Pickard working at AT&T for the crystal detector used to detect radio waves. Known as the cat's whisker it used the rectifying properties of the contact between a fine wire and certain metallic crystals, previously described by Braun, in what we would now call a point contact diode. Pickard typically used Silicon Carbide (carborundum) crystals. The same year United States Army General Henry H.C. Dunwoody also patented a crystal detector device based on carborundum.

1907 Leo Hendrik Baekeland a Belgian immigrant in the USA investigating new materials for electrical insulation invented Bakelite, or "Oxybenzylmethylenglycolanhydride" to give it its Sunday name, the first thermosetting plastic which was later used to manufacture everything from telephone handsets to costume jewellery.

1907 American inventor Lee De Forest invents the audion tube (valve). Now called the triode it was conceived as an amplifier but later used also as a switch. It was the first active electronic device.

1907 Henry Joseph Round an English radio engineer working for Marconi in New York, wrote to the "Electrical World" magazine with "A Note on Carborundum" describing his discovery that the crystal gave out a yellowish light when 10 Volts was applied between two points on its surface and that other crystals gave off green, orange or blue light when excited with voltages up to 110 Volts. He had inadvertently stumbled across the phenomenon on which the Light Emitting Diode (LED) depends, but there was not enough light to be useful and silicon carbide being hard to work with and Round's discovery was mostly forgotten. The phenomenon was rediscovered by Losev in 1922 and again by Holonyak in 1962.

1907 French physicist Pierre Ernst Weiss postulated the existence of an internal, "molecular" magnetic field in magnetic materials such as iron with molecules forming into microscopic regions he called magnetic domains within which the magnetic fields due to atoms are aligned. Under normal conditions domains themselves are randomly oriented and they have no magnetic effect. However, when they are put in a magnetic field, they tend to align themselves with the magnetic field causing the material to exhibit magnetic properties.

The concepts of paramagnetism and diamagnetism were first defined by Faraday in 1846. Magnetic properties are now understood to be a result of electric currents that are induced by the movement of the electrons in individual atoms and molecules. These currents, according to Ampere's law, produce magnetic moments in opposition to the applied field. The electron configuration in the atoms determines its magnetic properties whether diamagnetic or paramagnetic.

Diamagnetic materials, when placed in a magnetic field, have a magnetic moment induced in them that opposes the direction of the magnetic field. Paramagnetic behaviour results when the applied magnetic field lines up all the existing magnetic moments of the individual atoms or molecules that make up the material. This results in an overall magnetic moment that adds to the magnetic field. Pierre Curie showed that paramagnetism in nonmetallic substances is usually characterized by temperature dependence; that is, the size of an induced magnetic moment varies inversely to the temperature. Weiss's domains apply to ferromagnetic substances like iron which retains a magnetic moment even when the external magnetic field is removed. The strong magnetic effect causes the atoms or molecules to line up into domains. The energy expended in reorienting the domains from the magnetized back to the demagnetised state manifests itself in a lag in response, known as hysteresis. Ferromagnetic materials lose their magnetic properties when heated, the loss becoming complete above the Curie temperature.

1907 After almost 3000 years of use in various forms, the first patent for the process of silk screen printing or serigraphy (from the Latin "Seri" - silk) was awarded to English printer Samuel Simon of Manchester. Although the use of a rubber bladed squeegee to force the ink through the stencil was already known, he is generally credited with the idea of using silk fabric as a screen or ground to hold a tieless stencil. Screen printing derives from the ancient art of stenciling used by the Egyptians as early as 2500 B.C. and refined by the Chinese in the seventh century A.D.. Screen printing is arguably the most versatile of all printing processes, able to print on any surface, with any shape or contour and any size. Although the silk mesh has been replaced by more durable or stable materials such as polyester and perforated metal screens, the technique is still used extensively in the electronics industry today for printing thick film and thin film circuits, for printing the etching patterns for printed circuit board tracks and for the precision application of conductive and other adhesives for making connections and mounting components on surface mounted printed circuit boards as well as for the conventional printing of logos, designs and text on both components and packaging.

1908 Construction of the first German pumped storage power plant and of hydraulic research centre in Brunnenmuehle in Heidenheim by Voith Turbo. Since then many more pumped storage systems have been installed throughout the world. The hydraulic battery.

1908 Swiss textile engineer Jacques Edwin Brandenberger invented Cellophane, made from the cellulose fibres of wood or cotton. It is used as a separator in batteries particularly in silver oxide cells.

1909 Danish biochemist Søren Peter Lauritz Sørensen introduced the concept of pH as a measure of the acidity or alkalinity of a solution.

1909 Hermetically sealed wet battery introduced by Beautey in France.

1910 American Robert Millikan determined the charge on the electron by means of his Oil Drop experiment.

In 1897 John S.E. Townsend one of J.J. Thomson's research students, and in 1903 Thomson himself with H.A. Wilson (no relation to the inventor of the "Cloud Chamber"), had measured the charge on the electron with a similar method using a water cloud but their results were inaccurate. Millikan adapted this technique with some ingenious (and some not so ingenious) changes to measure e to within a 0.4% accuracy. A fine mist of oil drops was introduced into a chamber in which the air was ionised by X-rays. From the ionised gas some electrons attach themselves to some of the oil droplets. At the top of the chamber was a positively charged plate with a corresponding negative plate at the base. Charged droplets (with electrons) were attracted upwards to the positive plate while uncharged droplets fell downwards under the influence of gravity. By adjusting the voltage between the plates the electrical field could be varied to increase or decrease the upward force on the charged droplets. The voltage was adjusted so that the charged particles appeared stationary at which point the electrostatic force just balanced the gravitational force. The charge on the electron could then be calculated from a knowledge of the electrical field and the mass of the oil droplet determined by the speed at which it falls. Since the magnitude of the e/m ratio had already been determined by J.J. Thomson, the experiment also allowed the mass of the electron to be determined. From his work we know that the electron has a charge of -1.6 X 10^-19 Coulombs and a mass of 9.1 X 10^-31 Kg, which is only 0.0005 the mass of a proton. From this we can derive that a current of 1 Amp (1 Coulomb per second) is equivalent to an electron flow of 6.3 X 10¹⁸ electrons per second.

Although Millikan's method was beautifully simple, his published conclusions did not truly reflect the results of the measurements made. He was selective in choosing the results, discarding two thirds of the measurements made because they did not support his conclusions, at the same time improving the accuracy of the experiment. He was right, but it took others to prove it conclusively.

Millikan initially studied classics and worked as a teacher and administrator. He did not begin to do research seriously until he was almost forty. He eventually was awarded the Nobel prize for his determination of Planck's Constant.

1910 William David Coolidge working at General Electric in the USA invented the tungsten filament which greatly improved the longevity of the light bulb.

1910 Neon lighting using the techniques discovered by Plücker and Hittorf and the newly discovered neon gas was patented by French experimenter Georges Claude. Substituting different gases allowed a range of colours to be produced. Although the neon lights were used for advertising in France it was not until 1923 that they were brought to the USA by Packard car dealer Earl Anthony.

1911 Superconductivity was first observed in mercury by Dutch physicist Heike Kamerlingh Onnes of Leiden University. When he cooled it to the temperature of liquid helium, 4 degrees Kelvin, its resistance suddenly disappeared.

1911 The experiment on radioactivity that contributed most to our knowledge of the structure of the atom was done by Rutherford, who with Soddy had previously identified the atomic radiation emitted by Uranium and explained the phenomenon of radioactive transformation. Working at the University of Manchester with his students Hans Geiger (later famous for his "Counter") and Ernset Marsden, Rutherford bombarded a thin foil of gold with a beam of alpha particles (Helium nuclei) and looked at the beams on a fluorescent screen. They noticed that most of the particles went straight through the foil and struck the screen but some (0.1 percent) were deflected or scattered in front (at various angles) of the foil, while others were scattered behind the foil.

Rutherford concluded that the gold atoms were mostly empty space which allowed most of the alpha particles through. However, some small region of the atom must have been dense enough to deflect or scatter the alpha particle. He called this dense region which comprised most of the mass of the atom the atomic nucleus and proposed the model of an atom with a nucleus and orbiting electrons. Awarded a Nobel prize for his work on the structure of the atom, he famously said "The energy produced by the breaking down of the atom is a very poor kind of thing. Anyone who expects a source of power from the transformation of these atoms is talking moonshine. " If he didn't believe Einstein, he could have at least profited from advice from another of his students, Niels Bohr (1913 below).

1911 In an address to the Röntgen Society, Scottish engineer Alan Archibald (A.A.) Campbell Swinton described in detail the workings of a proposed all electronic television system using a cathode ray tube scanning an array of photocells onto which the image was projected for the transmitter and another cathode ray tube scanning a fluorescent screen as the receiver. This was at a time when the possibilities of radio communication had just been discovered, radio valves were practically unknown, photocells were most inefficient and vacuum technology was still very primitive. Due to obvious difficulties at the time the system was never constructed. It was left to another Scottish inventor, John Logie Baird to demonstrate the first working television system in 1926. It was an electromechanical system based on the Nipkow disc image scanning system. Although Baird's system was used in 1929 for the first public broadcasts in the UK, electromechanical systems proved to be a dead end.

1912 J J Thomson and Frederick Soddy discovered isotopes by observing the different parabolic paths traced by ions of different mass when passing through electric and magnetic fields. Soddy formulated the concept of isotopes, for which he was awarded a Nobel Prize in 1921. It states that certain elements exist in two or more forms which have different atomic weights but which are indistinguishable chemically. They used this phenomenon to construct the first Mass Spectrometer (then called a parabola spectrograph), a tool that allows the determination of the mass-to-charge ratio of ions and the identification of the different compounds contained in chemical samples. The Mass Spectrometer has since become an ubiquitous research tool in chemistry.

1912 Charles Kettering in the USA invented the first practical self-starter for automobiles, originally patented by Dowsing in 1896. The subsequent adoption by General Motors of battery-started cars provided the impetus for massive growth in the demand for lead acid batteries spawning new developments and performance improvements. See Willard 1915.

1912 Australian born Sir William Lawrence Bragg working with his father British physicist William Henry Bragg at Cambridge University discovered X-ray diffraction and formulated Bragg Law to quantify the phenomenon, thus founding the study of X-ray crystallography. The process is used to analyse crystal structure by studying the characteristic patterns of X-rays that deviate from their original paths because of deflection by the closely spaced atoms in the crystal. This technique is one of the most widely used structural analysis techniques and plays a major role in fields as diverse as structural biology and materials science. X-ray crystallography is used in battery design to analyse alternative chemical mixes and the associated crystal structures to optimise the physical and chemical characteristics of the active chemical contents in the cells. The ability to study the structure of crystals marked the origin of solid-state physics and provided a vital tool for the development of today's semiconductor industry.

1912 German physicist Max von Laue proved that X-rays are electromagnetic waves with a wavelength shorter than or of the same order as the separations between the ordered atoms in a crystal by examining the interference or diffraction effects that could be observed when an X-ray beam hits layers of atoms in a crystal. The wavelength observed was about 1000 times shorter than the wavelength of light. Von Laue was given the 1914 Nobel Prize for his discovery of diffraction of X-rays

1912 Scottish physicist Charles Thomson Rees Wilson devised the Wilson cloud chamber as a means of making the tracks of ionising radiation visible in order to detect sub atomic particles such as protons and electrons and other ionising radiation. It consisted of a closed container filled with a supersaturated vapour such as water in air. When ionising radiation passes through the vapour, it leaves a trail of charged particles (ions) that serve as condensation centres for the vapour which condenses around them. The path of the radiation is thus indicated by tracks of tiny liquid droplets in the supersaturated vapour

1912 Twenty one year old Russian immigrant David Sarnoff was working as a telegraph operator at the Marconi Wireless station in New York when SOS signals from the sinking S.S. Titanic came in from the frozen North Atlantic. Staying at his post relaying messages for 72 hours straight brought him instant fame. The experience convinced him of the potential of radio and he went on to found the Radio Corporation of America RCA.

1913 Neils Bohr a Danish physicist working under Rutherford in Manchester applied quantum theory to molecular structure proposing a more detailed model of the atom with electrons existing in orbits that had discrete quantised energies, or specific energy levels. He proposed that the chemical properties of the element are largely determined by the number of electrons in the outer orbits and introduced the idea that an electron could drop from a higher-energy orbit to a lower one, emitting a photon (light quantum) of discrete energy. This became the basis for quantum mechanics for which he was awarded a Nobel prize in 1922.

In contrast to his mentor Rutherford, Bohr is quoted as saying "Prediction is very difficult, especially about the future"

1913 Young English Physicist Henry Gwyn Jeffreys Moseley working with Rutherford at Manchester explained for the first time the fundamental pattern underlying the periodic table. Using X-ray spectra obtained by diffraction in crystals bombarded with cathode rays, he found that the heavier the atomic mass of the element, the shorter was the wavelength and the more penetrating were the X-rays emitted, indicating a systematic relationship between the wavelength of the X-rays and the atomic mass of the element. (X-rays are generated when a focused electron beam accelerated across a high voltage field bombards a stationary or rotating solid target). He determined that the positive charge on the nuclei of the atoms always increases by 1 in passing from one element to the next in the periodic table and he called this the atomic number. Moseley's discovery showed that atomic numbers were not arbitrary as had previously been thought, but followed an experimentally verifiable pattern. He predicted the existence of two new elements, now known to be radioactive, non-naturally-occurring technetium and promethium, by showing that there were gaps in the sequence at numbers 43 and 61.

Like many other patriotic youths at the time Moseley volunteered to serve in the First World War and was killed at Galipoli at the age of 27.

1913 Patent filed by Arthur Berry for etched printed circuits used in heaters. Similar subtractive techniques were also proposed by Littlefield and E. Bassist using photoengraving and electrodeposition of copper but the ideas do not appear to have caught on.

1913 Henry Ford introduced the moving conveyor line for assembly operations. Also called the paced production line, in conjunction with better materials flow to each work place, it enforced work rate and line discipline enabling major efficiency gains to be achieved. It was not popular but the huge reductions in assembly time enabled Ford to pay higher wages. Paced production lines are now the norm for producing high volumes of high labour content products.

1914 Using the photoelectric effect Millikan determined Plank's constant directly - verifying the 1905 Einstein theory of the photoelectric effect and the quantum nature of light. (After ten years trying to prove Einstein's photon or particle theory that light was wrong, he eventually succeeded in proving it was right.) He was awarded the Noble prize for this work in 1923.

1915 American physicist Manson Benedicks discovers the rectifying properties of germanium crystals, a discovery that will ultimately lead to the development of the "semiconductor chip".

1915 Improvements to automotive lead acid SLI battery reliability and safety introduced by Willard Storage Battery Company including rubber plate separators and shortly afterwards hard rubber cases. Previously lead acid battery designs had been diverse and unreliable with cases and separators constructed from a variety of materials such as wood dipped in asphalt, waxed leather, ceramics and glass. For the next 30 years or more, until the availability of easily moulded plastics, the construction of automotive batteries was based on design concepts introduced by Willard.

1915 During the First World War, batteries became essential for powering torches and particularly military field telegraph equipment but the source of pyrolusite from which is derived the manganese dioxide, needed for Leclanché cells, was controlled by the Germans and an alternative had to be found. In response, French physicist Charles Fery developed an alternative air depolarising battery. The cathode was a large porous carbon pot, only partially filled by the zinc anode and the electrolyte was open to the air. The design essentially diluted the polarisation effect of the hydrogen generated and promoted contact with the oxygen in the air for recombination into water. It was not very efficient but although it was not perfect it served its purpose and 1.5 million were produced. It could be considered the forerunner of the Zinc-Air battery.

1915 Western Electric engineer Edwin H. Colpitts patented the push-pull amplifier. The design used a phase splitter to separate the positive going part of the wave form from the negative going part and amplified the two parts in separate valves (tubes). After amplification the two parts were recombined to reconstitute the waveform. Since two valves were used the design permitted higher power outputs to be achieved and at the same time, because the voltage swing in each valve was lower, the circuit provided linear amplification free from distortion.

1915 American engineer Ralph Vinton Lyon Hartley working at Western Electric invents the variable frequency Hartley oscillator which can be tuned using a variable capacitor. Oscillation is induced by positive feedback around a valve (tube) amplifier. The frequency of oscillation is determined by two inductors (or a tapped single inductor) and a single capacitor. Modern versions use transistors or operational amplifiers to provide the amplification.

The same year fellow Western Electric engineer E. H. Colpitts (see above) invented an alternative oscillator with slightly better frequency stability. It is the electrical dual of a Hartley oscillator using two capacitors and one inductor determine the frequency.

1916 American chemist Gilbert Newton Lewis advanced Frankland's theory of valency and established the basis of the theory of chemical bonding by proposing that chemical bonds are formed between the atoms in a compound because electrons from the atoms interact with each other. He had observed that many elements are most stable when they contained eight electrons in their valence shell and suggested that atoms with fewer than eight valence electrons bond together to share electrons and complete their valence shells.

The compounds used in batteries consist mainly of metal and non-metal atoms held together by ionic bonding in which electrons are completely transferred from one atom to another. The atoms losing a negatively charged electrons form positively charged ions, while the atoms gaining electrons become negatively charged ions. The oppositely charged ions are attracted to each other by electrostatic forces which are the basis of the ionic bond. This explains the theory of dissociation proposed by Arrhenius in 1884.

1916 German physicist Arnold Johannes Wilhelm Sommerfeld enhanced the Bohr theory of the atomic structure by introducing non-circular orbits, by allowing quantised orientations of the orbits in space, and by taking into account the relativistic variation in the mass of the electron as it orbited the nucleus at high speed. These properties or quantum states were characterised by three quantum numbers in what is now called the Bohr-Sommerfeld model of the atom.

1916 1916 Edwin Fitch Northrup working at Princeton University invents the coreless high frequency induction furnace.

1916 Metallurgist Jan Czochralski, born in Kcynia, Western Poland, then part of Prussia (Germany), working in Berlin accidentally discovered a method of drawing single crystals when when he absent mindedly dipped his pen into a crucible of molten tin rather than his inkwell. On pulling the pen out he discovered that a thin thread of solidified metal was hanging from the nib. Experimenting with a capillary in place of the nib, he verified that the crystallized metal was a single crystal and went on to develop the technology for producing large single crystals, still a fundamental process for semiconductor fabrication today.

At the request of the president of Poland, in 1928 he moved back to Poland to take up the post of Professor of Metallurgy and Metal Research at the Chemistry Department of the Warsaw University of Technology where he published many papers. However after World War II he was unjustly accused of aiding the Germans during the war and stripped of his professorship. Although he was later cleared of any wrongdoing by a Polish court, he returned to his native town of Kcynia where he ran a small cosmetics and household chemicals firm until his death in 1953.

The Czochralski (CZ) method of growing single crystals was adopted in 1950 by Bell Labs and is used today in 95% of all semiconductor production.

1917 American engineer George Ashley Campbell awarded patents for low pass, high pass and band pass filters consisting capacitors and inductors. These passive electric wave filters had already been employed for several years in the telecommunications industry for signal conditioning, selection and tuning and similar designs had been developed in Germany by K W Wagner in 1915.

1917 Rutherford bombarded Nitrogen gas with naturally occurring alpha particles (Helium nuclei) from radioactive material and obtained atoms of an Oxygen isotope and positively charged particles with a higher energy which he called protons (Hydrogen nuclei, isolated for the first time). He had split the atom, creating the world's first nuclear reaction, albeit a weak one. Rutherford had achieved the alchemist's dream of transmuting matter, which led to the work on nuclear fission.

Rutherford did not publish the results of this experiment until two years later in 1919. He continued his investigations with Cockcroft and Walton who started work in 1928 on a controlled source of high energy particles which enabled them probe deeper into the atomic structure.

1918 American engineer and inventor Edwin Howard Armstrong patented the superheterodyne radio receiver solving the problem of providing a wide tuning range and high selectivity between stations. This was achieved by using a variable frequency local oscillator or frequency changer to shift the signal (carrier wave plus sidebands) of the desired transmitter to a convenient fixed intermediate frequency (IF). Tuning takes place in a separate narrow band IF amplifier which only needs to be tuned to a single frequency.

German engineer Walter Schottky also independently invented a superheterodyne radio receiver the same year.

A simple version of the idea had been used by Fessenden in 1901 but he had not developed it. He did however give the circuit its name from the Greek heteros (other) and dynamis (force). Until the digital age and phase locked loops, the superheterodyne principle was used in 98% of all radios world wide.

1918 A. M. Nicholson working at Bell Labs patents the crystal oscillator. When a varying signal is applied across the crystal it expands and contracts in sympathy. The crystal oscillator circuit sustains oscillation by taking a voltage signal from the crystal, amplifying it, and feeding it back to the crystal which resonates at a certain frequency determined by its cut and size. Today more than 2,000,000,000 quartz crystals are produced annually for use in electronic circuits needing precise frequency control including radio tuners, mobile phones, computers, clocks and watches.

1918 Max Schoop produced high current printed circuit boards with heavy tracks for high power vacuum tube circuits using metal deposition by flame spraying through a mask. While successful, like Berry's ideas before him, they were not taken up by others.

1919 The flip-flop or bi-stable latch circuit a basic building block in all digital computers and logic circuits was invented by British engineers William Henry Eccles and F.W. Jordan working at the government's National Physical Laboratory. Originally implemented with triodes, now with transistors (diagram), it can remember two possible conditions or states and thus is able to store a single bit of information or a binary digit, thus enabling computers to count. This was the circuit chosen in 1958 by Robert Noyce for the first planar Integrated Circuit.

Eccles and Jordan were not Americans as reported on many US based web sites. Another internet myth. Eccles did pioneering work on radio propagation and was a Fellow of the Royal Society (FRS). He rose to be President of the Physical Society from 1928 to 1930, and President of the Institute of Electrical Engineers (IEE) in 1926. Jordan faded into obscurity.

1919 The Electret, the electrostatic equivalent of the permanent magnet, was discovered by Mototaro Eguchi in Japan. Electrets are dielectric materials that have been permanently electrically charged or polarised. They are produced by heating certain dielectric materials to a high temperature and then letting them cool while immersed in a strong electric field. The materials are composed of long molecule chains, each with an electric dipole moment which can be formed into electrostatic domains similar to the magnetic domains found in magnets. Electret foils are commonly used in microphone transducers since they do not require a polarising voltage to be applied as in "condenser" microphones.

1919 The tetrode valve was invented by Walter Schottky who discovered that by placing a grid between the anode plate and the control grid of a triode valve, the grid-plate capacitance was reduced to almost one-hundredth of that in the triode. The second grid acted as a screen to prevent the anode voltages from affecting the control grid and eliminated instability (oscillation) caused by anode-grid feedback in the triode valve.

1920 The first regular commercial radio broadcasts by KDKA in Pittsburgh. By the end of 1922 a further 563 licensed A.M. radio stations are operating.

1920's Diesel electric locomotives first introduced with electric drives providing the transmission mechanism eliminating the need for a clutch and a gearbox. (Electric drives provide maximum torque at zero speed. Internal combustion engines can only provide driving torque when they are running at speed)

1922 The BBC was formed in the UK by a group of leading "wireless" manufacturers including Marconi and started a radio broadcast service. Widespread radio broadcasting started around the same time in many countries throughout the world bringing wireless into the heart of many homes and with it a new demand for batteries to power them.

1922 Light emission from silicon carbide diodes was rediscovered in the Soviet Union by self taught Oleg V. Losev. He produced a range of high frequency oscillating, amplifying and detector diodes using zinc oxide and silicon carbide crystals about which he published 16 papers on the underlying theory of operation and was awarded ten patents on Light Emitting Diodes (LED)'s, photodiodes and optical decoders of high frequency signals.

Even more amazing was his discovery of the negative resistance (dI/dV) characteristic that can be obtained from biased point-contact zincite (ZnO) crystal diodes and the possibility of using this negative resistance region to obtain amplification, anticipating the tunnel diode. See negative resistance characteristic. He used these properties to construct fully solid-state RF amplifiers, detectors and oscillators at frequencies up to 5MHz a quarter century before the invention of the transistor.

He designed and constructed over 50 radio receivers, incorporating his own tuning, heterodyning and frequency converting circuits and built a production line to produce his cristadyne radio receivers, powered by 12 Volt batteries, thirty years before the transistor radio. Interstage interaction inherent in using two-terminal devices to obtain gain and adjusting the cat's whiskers were problematical but the radios worked. These problems together with the difficulties of obtaining zincite which was found in commercially significant quantities in only two mines, both in New Jersey, USA led to Losev eventually abandoning the crystadyne.

Losev starved to death during the siege of Leningrad in 1942 and the original records of his works were lost.

1922 After the 1917 Russian revolution, naval engineer Nicholas Minorsky emigrated to the USA where he worked with Steinmetz. Using his knowledge of automatic steering of ships, in 1922 he published a paper "Directional stability of automatically steered bodies", outlining the principles of 3 term controllers, the basis of modern PID control systems.

1922 German organic chemist Hermann Staudinger published his theories on polymers and polymerisation. He showed that natural rubbers were made up of long repetitive chains of monomers that gave rubber its elasticity and that the high polymers including polystyrene manufactured by the thermal processing of styrene were similar to rubber. Staudinger won the Nobel Prize for Chemistry for his research.

Polystyrene was originally discovered in 1839 by German apothecary Eduard Simon however he was not aware of its significance. It was first produced on an industrial scale by IG-Farbenindustrie in 1930

1923 The Marconi Company in Britain claimed to have made the first practical hearing aid called the Otophone. It used a carbon microphone and valve (vacuum tube) amplifier but with batteries it weighed an unpractical 7 Kg. It was not until 1953 with the advent of transistors and button cells that electronic hearing aids became truly practical.

1923 Quality engineers from the Western Electric Company working on sampling inspection theory developed graphs showing the probabilities of acceptance and rejection for different sampling plans. They identified the concepts of Consumer's Risk, the probability of passing a lot submitted for inspection which contains the tolerated number of defectives and Producer's Risk, the probability of rejecting a lot submitted for inspection which contains the tolerated percentage of defects. In 1926 they produced the first set of Sampling Inspection Tables for single and double sampling followed in 1927 by tables for determining the Average Outgoing Quality Limit (AOQL). The tables were published by Harold F. Dodge and Harry J. Romig in 1944 however these sampling and control techniques had already found wider use during World War II when standard military sampling procedures for inspection by attributes were developed by the US military and eventually published as Mil Std 105A in 1950.

The tables and techniques were designed to facilitate better production control, more efficient inspection and to avoid disputes and were very effective in achieving these goals over many years. Unfortunately they also encouraged the notion that faults were inevitable and the idea of an acceptable quality level placed a limit on aspirations to do better, effectively giving a licence to ship a few defects so long as the AOQL was acceptable. An example of "The Law of Unintended Consequences". The danger of these attitudes was finally realised in the 1980's when the public noticed that the Japanese, following principles introduced by W. E. Deming, coupled with Japanese work ethics, produced products which were significantly better than western offerings. Working to Six Sigma quality standards has been the West's response to the Japanese challenge of TQM.

1923 Danish chemist Johannes Brønsted and simultaneously British chemist Thomas Lowry proposed the Brønsted - Lowry concept of Acids and Bases which states that: An acid is a molecule or ion capable of donating a proton (That is a hydrogen nucleus H⁺) in a chemical reaction , while a base is a molecule or ion capable of accepting one. More simply: An acid is a proton donor and a base is a proton acceptor.

The same year Lewis proposed a more generalised concept which states: An acid is a molecule or ion that can accept a pair of electrons while a base is a molecule or ion that can donate a pair of electrons. This explains why metal oxides are basic since the oxide ion donates two electrons while non-metal oxides which accept two electrons to share with the non-metal atom are acidic.

1924 German psychiatrist Hans Berger was the first person to prove the existence of so called brain waves, electric potentials or voltage fluctuations in the human brain, using an an electroencephalograph to detect and amplify the signals. He experimented by attaching electrodes to the skull of his fifteen year old son Klaus, recording the first human electroencephalogram (EEG).

1924 French aristocrat who came to physics late in life, Prinz Louis-Victor Pierre Raymond, duc de Broglie, speculated that nature did not single out light as being the only matter which exhibits a wave-particle duality. He proposed that since light waves could be considered as particles the converse should be true and ordinary ``particles'' such as electrons, protons, or bowling balls could also exhibit the characteristics of waves.

1924 The modern, moving coil, direct radiator, loudspeaker patented by Western Electric (Bell Labs) engineers Chester W. Rice and Edward Washburn Kellogg.

1924 The ribbon microphone and its converse the ribbon loudspeaker were invented by German engineers Walter Schottky and Erwin Gerlach working at Siemens. The ribbon microphone was constructed from an extremely thin concertina ribbon of aluminium placed between the poles of a permanent magnet.

1925 Electrical recording using a microphone, an amplifier using De Forest's Audion vacuum tube (valve) and an electrical disc-cutting head, in a system invented the previous year by Joseph P. Maxfield and Henry C. Harrison of Western Electric, was adopted by the Columbia and Victor record companies. Electrical playback also became available the same year using amplifiers and the Rice-Kellogg loudspeaker.

What is surprising is that the basic technologies for implementing electrical recording and play back had been available in the telephone industry since 1877 when Edison invented the phonograph but for almost fifty years the record industry had persevered with Edison's system of direct acoustic recording on to wax cylinders or discs using large recording horns which both limited and dominated the recording environment. Similarly playback was had remained mechanical over the same period using clockwork motors, acoustic pick-ups and clumsy horns which gave out limited sound volume.

1925 Between 1925 and 1935 American engineer and politician Vannevar Bush and colleagues developed a series of analogue computers which they called differential analysers. They were capable of solving differential equations with up to eighteen independent variables and were based on interconnected mechanical integrators constructed from gears and mechanical torque amplifiers with the output represented by distances or positions. The 1935 version weighed 100 tons and contained 2000 vacuum tubes, 150 motors, thousands of relays and 200 miles of wire. Processing analogue data is a key requirement of modern control systems, however analogue values can now be represented electrically and processed in linear integrated circuits or converted to digital form for manipulation by microprocessors.

1925 Swiss theoretician Wolfgang Pauli explained why electrons orbiting an atomic nucleus do not all fall into their lowest energy state due to attraction from the positive protons in the nucleus. He proposed that besides orbiting the atomic nucleus, as in the three state model proposed by Neils Bohr and Arnold Sommerfeld, the electrons also have spin properties. Thus the electron can have four quantum states characterised by 4 quantum numbers which define, the distance of the electron from the nucleus, its kinetic energy (based on its angular momentum), its magnetic moment (based on the azimuth angle of the plane of the orbit) plus the intrinsic magnetic moment of the electron itself due to its spin. He further proposed the principle that no two electrons in an atom can occupy the same quantum state, now known as the Pauli Exclusion Principle. This principle also provided the theoretical basis for the Mendeléev's Periodic Table of Elements.

Pauli was awarded the Nobel Prize in 1945 for his discovery of a new law of Nature.

One of the giants of twentieth century theoretical physics Pauli was notorious for his rudeness. He was also known for the "Pauli Principle" which predicted disaster for any piece of apparatus with which he was involved.

1925 German physicist Werner Heisenberg proposed a new model for the structure of the atom with different quantised energy states represented by frequencies and intensities. At the suggestion of Max Born these were incorporated into matrices. Known as Matrix Mechanics theory, it was a mathematical abstraction, but based on observable qualities of the atom, since current methods at describing the atom with physical analogues of orbiting electrons could not account completely for its behaviour.

Heisenberg was appointed to be head of Germany's atomic weapons programme during World War II and although, through the pioneering work of Szilard, Hahn and Strassmann on nuclear fission, Germany was ahead of the Allies before the war, by 1945 they were still a long way from being able to produce an atomic bomb and never even achieved a chain reaction.

1925 Charles Ducas described a variety of practical ways for manufacturing printed circuits including etching, electroplating and printing with conductive inks. He also proposed multilayer circuit boards and showed how to implement connections between the layers.

1926 Frenchman Cesar Parolini devised improved additive printing and plating techniques for printed circuit manufacturing methods, some of which had been described years before, but not implemented by Edison.

1926 Waldo L. Semon an American chemical engineer invented plasticised poly vinyl chloride (PVC). The plasticisers are smaller, oily molecules interwoven with the long polymer chains which allow them to slide over eachother and give the plastic its characteristic flexibility. Without these plasticiser additives PVC would be too brittle. Originally discovered by Baumann in 1872 PVC is now used extensively for insulating wires and cables.

1926 German engineers Eckert and Karl Ziegler patent first commercial injection moulding machine.

1926 Building on de Broglie's wave - particle duality hypothesis Austrian physicist Erwin Schrödinger formulated a theory for the behaviour of atomic particles which has the same central importance to Quantum Mechanics as Newton's laws of motion have for the large-scale phenomena of classical mechanics. Schrödinger's Wave Equation was proposed as an alternative to Heisenberg's Matrix Mechanics. It describes the atom in the form of the probability waves (or wave functions) that govern the motion of small particles, and it specifies how these waves are altered by external influences. He realized that the possible orbits of an electron would be limited to those accommodating standing waves, that is, with an exact number of wavelengths. This permits only a limited number of possible orbits and no possible orbits between them. Schrödinger's theory of Wave Mechanics explained the hitherto inexplicable behaviour of atomic particles by considering them as waves not particles and the wave equation predictions were borne out by experimental results. He considered his model closer to classical physical theory and less of an abstraction than Heisenberg's model. Paul Dirac later proved that these two models were equivalent.

Schrödinger contributed to many branches of physics including quantum theory, optics, kinetic theory of solids, radioactivity, crystallography, atomic structure, relativity and electromagnetic theory. In 1935 he published the famous Schrödinger's cat paradox which was designed to illustrate the absurdity of the probabilistic notion of quantum states. This was a thought experiment where a cat in a closed box either lived or died according to whether a quantum event occurred. The paradox was that both universes, one with a dead cat and one with a live one, seemed to exist simultaneously until an observer opened the box. In his later years he applied quantum theory to genetics. He coined the term "Genetic code"and published an influential book "What is Life" which inspired Watson and Crick in their search for the structure of DNA. He also studied Greek science and philosophy and published his thoughts in his book "Nature and the Greeks".

Schrödinger's wave mechanics provided the foundation, built on by Heisenberg, Dirac and others, for explaining the behaviour of electrons, nuclei, atoms, molecules and chemical bonding, fundamental building blocks or processes used in galvanic cells, as well as nanotechnology and the phenomena of nuclear fusion and superconductivity, processes used in the generation and distribution of electric power. Quantum mechanics also represents behaviour of electrons and "holes" (the absence of electrons) in semiconductors and the process of electron tunneling used in Scanning Tunneling Microscopes and other electronic devices. For the future, research into the possibilities of quantum computers whose bits can be both 0 or 1 at the same time, depending on the electron spin, performing calculations at unprecedented speed are also founded on the quantum theories of Schrödinger, Heisenberg, Dirac and their successors.

It was almost forty years before before the principles demonstrated by Volta in his voltaic pile were successfully put to use by the telegraph pioneers in commercial products. In the case of Faraday's motor, it was almost sixty years before a market was created. Watch out for Schrödinger's kittens.

A man of many accomplishments Schrödinger's life was both colourful and complicated. He had an informal manner and throughout his life he travelled with walking boots and rucksack which raised a few eyebrows at the many conferences he attended. He served in Italy and Hungary during the First World War. Later he was an opponent of Nazi rule in Germany which brought him several brushes with authority. As an eminent physicist he also received many offers of positions in the worlds best universities and at various times he help posts at Graz, Berlin, Breslau, Zurich, Oxford, Princeton, Edinburgh, Rome, Dublin, Gent and Vienna. His relationships with women were however even more wide-ranging. He had numerous lovers with his wife's knowledge (even more Schrödinger's kittens) and she in turn was the lover of one of Schrödinger's friends. While at Oxford he brought his colleague Arthur March from Germany to be his assistant since he was in love with March's wife who was pregnant with his child and he lived openly with his new daughter and two wives one of whom was still married to another man. During his time in Dublin he fathered two more daughters with two different Irish women.

1926 German physicist Max Born working at Cambridge found a way to reconcile particles with waves by treating Schrödinger's wave as the probability that an electron will be in a particular position.

1926 German professor of physics at Leipzig University, Julius Edgar Lilienfeld emigrated to the USA and filed a patent for what would today be called a field effect transistor. It consisted of a semiconducting compound sandwiched between two metal plates, one of which was connected to a current source and the other connected to the output. The resistance of the semiconductor between the plates could be varied by means of a variable electric field created across it by a control signal connected to a third plate at the side of this sandwich and insulated from it. It worked in a way analogous to a vacuum tube and in 1930 Lilienfeld was granted a patent for "A method and apparatus for controlling electric currents". Other than Lilienfeld, nobody at the time seems to have recognised the device's potential and it faded into obscurity until it was rediscovered by William Shockley's patent attorneys, much to Shockley's chagrin when he independently conceived a similar device 20 years later.

1927 Heisenberg discovers the Uncertainty Principle. It is impossible to determine the position and momentum of a particle simultaneously. The more accurate one is measured, the more inaccurate the other becomes.

Einstein was very unhappy about this apparent randomness in nature. His views were summed up in his famous phrase, "God does not play dice".

1927 British physicist George Paget Thomson, son of J.J. Thomson, discoverer of the electron, working with Alexander Reid at Aberdeen University and simultaneously and independently, Americans Clinton Joseph Davisson working with Lester Halbert Germer at Western Electric Labs, confirmed de Broglie's hypothesis of the wave particle duality of the electron. Thomson created transmission interference patterns by passing an electron beam through a thin metal foil and Davisson created diffraction patterns of electron beams reflected from metallic crystals, both confirming the wave nature of the electron.

1927 German physicist Friedrich Hund was the first to notice the possibility of the phenomenon of quantum tunneling which he called "barrier penetration" a process by which a particle can appear to penetrate a classically forbidden region of space passing from point A to point B without passing through the intermediate points. This is a manifestation of de Broglie's wave - particle duality theory with the electron acting like a wave rather than a particle. The phenomenon can be characterised by Schrödinger's wave equation which tells us that the energy associated with an electron is not discrete but has a probabilistic level. As a consequence a certain number of electrons will have more than enough energy to jump an energy gap that would normally be too wide. The effect is that electrons appear to tunnel through a barrier which we would normally expect bar them.

1927 In the USA a Lead Acid car battery cost $70 while a typical car cost $700. Today a car battery still costs $70 while car prices have skyrocketed by comparison.

1927 Invention and patent application by French company Chauvin Arnoux for the "Contrôleur Universel", the forerunner to the Multimeter. Despite this patent, the invention was to become copied throughout the world.

1927 In the first technical analysis of a closed loop control system, American engineer Harold Steven Black working at Bell Labs demonstrates the utility of negative feedback in the design of telephone repeater amplifiers to reduce distortion. He thus established the theoretical basis of modern feedback control systems.

1927 Generic patent for flexible printed circuits as well as three dimensional circuits and printed inductors by applying conductive materials to a flexible substrate was published by Frederick Seymour.

1927 Mormon farm boy from Idaho, Philo Taylor Farnsworth conceived the idea of the world's first practical all electronic television system while still in high school. An electronic system had been proposed earlier by Campbell Swinton but due to the primitive state of the technology at the time it was never built. Farnsworth built a working system using the Farnsworth orthicon or image dissector tube and patented his design in 1927 while still only 21 and successfully fought off the patent claims from the mighty RCA. Nevertheless despite paying royalties to Farnsworth, RCA ultimately found ways around the patents and promoting their own man, Zworykin, as the originator of the television system they finally put Farnsworth out of business. Like Armstrong who had similar battles with RCA, Farnsworth's private life suffered and he became an embittered alcoholic in his early 30's. He spent much of his later life and all of his money in a fruitless pursuit of nuclear fusion.

1927 The Quartz Clock invented by Canadian born Warren Marrison working at Bell Labs. He demonstrated the superior accuracy of clocks using crystal controlled oscillators kept in time by the regular vibrations of a quartz crystal. Initially they were used for precise telecommunications frequency standards but today they are found in every battery powered quartz watch and they provide the microprocessor system clock in every personal computer.

1928 British physicist Paul Adrien Maurice Dirac working on quantum field theory at the Cavendish Laboratory in Cambridge combined the theories of quantum mechanics of Bohr and Pauli with Maxwell's electromagnetic field theory to model the properties of the electron. He introduced the concept of special relativity and electron spin, which gave the electron its internal magnetic properties and which Schrödinger had not been aware of, into Schrödinger's wave equation to develop the Dirac equation which was consistent with both Heisenberg's matrix mechanics and Schrödinger's wave theory. Dirac's model could treat the electron as either a wave or a particle and still get the right answers. It marked the beginning of Quantum Electrodynamics - QED.

In 1931, Dirac used his equation to predict the existence of a particle with the same mass as the electron but with positive rather than negative charge. This "anti-particle", now called a positron, was detected by American physicist Carl Anderson in 1932 and all particles are now known to have anti-particles.

Unlike Schrödinger, Dirac's shyness was legendary. When informed that he had won the Nobel Prize he told Rutherford that he did not want to accept it because he disliked publicity. Rutherford told him that refusing the prize would bring even more publicity!

1928 Swedish born American engineer Harry Nyquist formulates the Sampling Theorem which states that a signal can be exactly reproduced if it is sampled at a frequency F, where F is greater than twice the maximum frequency in the signal. Very important for specifying the sampling rate in monitoring and control systems. Nyquist went on to develop stability criteria for feedback control systems.

1929 The kinescope, a cathode-ray tube with all the features of modern television picture tubes invented by Russian born American, Vladimir Zworykin, working for RCA. In 1923 while working at Westinghouse, Zworykin applied for a patent on the iconoscope, a tube based on Campbell-Swinton's proposal of 1911, designed to create the images in his early television cameras but it was not used commercially and the patent was not granted until 1938. Zworykin was told by Westinghouse"to find something more useful to work on". The imaging technology on which television cameras were based is in fact descended from Farnsworth's image orthicon but RCA's PR machine claimed that Zworykin laid the foundations of today's television systems in 1923, ignoring the contributions of Farnsworth, the farm boy from Idaho who is almost forgotten today.

1930 The works of British physical chemist John Alfred Valentine Butler and German surface chemist Max Volmer on the theoretical basis of kinetic electrochemistry were summarised in the fundamental Butler-Volmer equation. It shows that the current flowing at an electrode is the sum of the anodic and cathodic contributions. It is also directly proportional to the area of the electrodes and increases exponentially with temperature.

1930 Russian Wladimir Gusseff invents Electro-Chemical Machining (ECM) using electrolytic erosion, a galvanic process essentially the reverse of electroplating which allows the machining of complex shapes in very hard metals. The work piece forms the anode and the shaped tool forms the cathode and they are supplied with a low DC voltage of about 40 Volts. Electrolyte is pumped through the gap between the tool and the work piece and metal is removed from the work piece in the vicinity of the tool by galvanic action as in a battery. The flowing electrolyte removes the dissolved metal so there is no tendency for it to be deposited on the cathodic tool.

Note This is different from the more common machining process known as Spark Erosion or Electro-Discharge Machining (EDM). In this process the work piece and the tool are immersed in a bath electrolyte, however the gap between the tool and the work piece is fed with a high frequency pulsating voltage which creates a spark across the gap which in turn vapourises the metal of the work piece in the proximity of the tool. It was invented by Russian brothers B.R. and N.I. Lazarenko in 1943.

Both of the above processes are used to make the intricate shapes used in injection moulding tools.

1930 Lilienfeld gave a paper on electrolytic capacitors before the American Electrochemical Society in which outlined the fundamental theories and practice for the design of these components, still in use today.

Electrolytic capacitors have a very high capacitance per unit volume allowing large capacitance values to be achieved making them suitable for high-current and low-frequency electrical circuits. The construction is similar to a spiral wound battery with two conducting aluminium foils, one of which is coated with an insulating oxide layer which acts as the dielectric, and a paper spacer soaked in electrolyte, all contained in a metal can. The aluminium oxide dielectric can withstand very high electric field strengths, of the order of 109 volts per metre, before break down. This allows the use of very thin dielectric layers to be used and this in turn permits a much larger area of the capacitive plates to be accommodated within the space inside the case. These characteristics enable very high capacitance values to be achieved.

The foil insulated by the oxide layer is the anode while the liquid electrolyte and the second foil act as cathode. They are thus polarized and so must be connected in correct polarity to avoid breakdown.

1931 Wallace Hume Carothers working at DuPont labs created Neoprene the first successful synthetic rubber. Neoprene's combination of properties, resistance to chemicals, toughness and flexibility over a wide temperature range made it suitable for the design of pressure vents which facilitated the construction of recombinant batteries and for gaskets used in battery enclosures. Searching for synthetic fibres Carothers also invented Nylon in 1935, now also used to produce a wide range of injection moulded components from containers to gears. In the USA, nylon stockings went on sale for the first time in 1940 and four million pairs were sold in the first few hours.

Carothers was a manic depressive alcoholic who, despite his great achievements, considered himself a failure. He founded and was head of Du Pont's research group working on polymers and polymerisation which was one of the most successful groups in the history of polymer science. He committed suicide in 1937 at the age of 41 by taking cyanide a year after his marriage and the untimely death of his sister.

1931 The portable Metal Detector patented by American engineer Gerhard Fischar. Metal detectors use a variety of methods to detect small changes inductance or perturbations in the local magnetic field when the detector is near to a metal object. See also Alexander Graham Bell's detector.

1931 Irish chemical engineer James J. Drumm introduces the alkaline Nickel Zinc Drumm traction battery after five years of development. A variant of the Michaelowski chemistry, they had a cell voltage of 1.85 volts and charge / discharge rates 40% higher than Nickel Iron cells with which they were intended to compete but they suffered from a low cycle life and high self discharge rate. Drumm built four trains to use his batteries but with the outbreak of World War II it became impossible to obtain both orders and raw materials and the company folded in 1940.

1931 French engineer H. de Bellescize applied for a UK patent for an improved homodyne radio tuning circuit. It was the first automatic frequency control (AFC) system and the first circuit to incorporate the basic features of a phase locked loop (PLL). The following year de Bellescize published a description of his design in "Onde Electrique", volume 11, under the title "La Réception Synchrone". The original homodyne receiver was designed in 1924 by a British engineer named F.M. Colebrook in an attempt to improve on Armstrong's superheterodyne receiver. Colebrook's design mixed the received signal with a locally generated sine wave at the same frequency as the carrier wave to extract the signal from the carrier in a simple detector - essentially a zero intermediate frequency (IF). De Bellescize improved on this by detecting any difference between the received carrier frequency and the local oscillator frequency and using the difference signal to adjust the oscillator frequency till it matched exactly the carrier frequency thus ensuring perfect synchronisation of the two signals and the desired zero IF. Further improvements to the design were made by british engineer D.G. Tucker and others and the tuner was renamed the synchrodyne.

The phase locked loop (PLL) is now a fundamental building block in synchronisation and control circuits and complete complete PLL circuits are available in low-cost IC packages.

1931 English engineer Alan Dower Blumlein invented stereo sound. A prolific inventor Blumlein made many advances in the field of acoustics and made significant contributions to Britain's first all electronic television service. During the war years he applied his considerable skills to Radar design. He died in a plane crash in 1942 at the age of 38 while testing the H2S Airborne Radar equipment for which he had designed many of the circuits. He was awarded 132 patents in his short life.

1932 German electrical engineers Max Knoll and Ernst August Friedrich Ruska invented the first transmission electron microscope (TEM). One of the first applications of quantum mechanics theory, it depends on wave properties of the electron rather than it's particle properties. Instead of a light beam, it used an electron beam which has a wavelength much shorter than a light beam and can thus provide a much higher resolution. Focusing was by means of magnetic coils acting as lenses and by 1933 a magnification of 7000 times was achieved, far in excess of what was possible with visible light. The beam is detected after passing through a very thin specimen to create an image. It is now an essential tool for investigating the structure of materials.

Fifty four years later Ruska was belatedly awarded a Nobel Prize jointly with Binnig and Rohrer in1986 in recognition of his fundamental work on electron optics and the invention of the electron microscope.

1932 First practical Fuel Cell system (Alkaline with porous electrodes) demonstrated by English mechanical engineer Francis Thomas Bacon, a direct descendant of Sir Francis Bacon, the 17th century philosopher.

1932 The Cavendish Laboratory's annus mirabilis. English engineer and physicist John Douglas Cockcroft and Irish physicist Ernest Thomas Sinton Walton, working under Rutherford at the Cavendish Laboratory, constructed the world's first nuclear particle accelerator for investigating atomic structures, now known as the Cockcroft-Walton accelerator, or more colourfully as an atom smasher. It was a 700,000 Volt linear accelerator which they used to bombard a Lithium target with protons (Hydrogen nuclei). Like many UK university experimenters at the time they had to improvise because of a shortage of resources, using amongst other things car batteries, and for the glass cylinders surrounding the electrodes they used glass tubes from petrol pumps they used Harbutt's plasticine to seal the joints in the vacuum tubes. Very high energies were needed to overcome the repulsion of the positively charged protons by the positively charged Lithium nucleus. The Lithium nucleus contains 3 protons and 4 neutrons. The high energy proton bombardment caused the Lithium nucleus to disintegrate into 2 alpha particles (Helium nuclei), each composed of 2 protons and 2 neutrons. This was the first disintegration of an atomic nucleus by controlled, artificial means, the first artificial nuclear reaction not utilizing radioactive substances, the first use of a particle accelerator to split the atom and the first artificial transmutation of a metal into another element.

In fact Rutherford had actually already split the atom in 1917 using a radioactive source, however he had merely knocked a proton out of the nucleus. Cockcroft and Walton had actually split it in two.

The speed of the resulting helium nuclei was measured and the kinetic energy calculated. It was found to be equivalent to the reduction in the combined mass of the resulting helium nuclei from the combined mass of the original lithium and hydrogen nuclei. This was the first verification of Einstein's law, E = mc².

The "Daily Express" headline on the news of their success was "The Atom Split, But World Still Safe".

1932 34 Years after the discovery of the electron and the proton, English physicist James Chadwick another of Rutherford's students working at Cambridge University finally isolates the Neutron confirming Rutherford's predictions of a heavy neutral particle twelve years earlier. Physicists soon found that the neutron made an ideal "bullet" for bombarding other nuclei. Unlike charged particles, it was not repelled by similarly charged particles and could smash right into the nucleus. Before long, neutron bombardment was applied to the uranium atom, splitting its nucleus and releasing the huge amounts of energy predicted by Einstein's equation E = mc². See Fermi (1942)

1932 Within seven months of the discovery of the neutron, Hungarian physicist Leo Szilard conceived of the possibility of a controlled release of atomic power through a multiplying neutron chain reaction and that this could be used to build a bomb. He fled Germany in 1933 to escape Nazi persecution and in 1934 filed a patent application for the atomic bomb, outlining the concept of using neutron induced chain reactions to create explosions and the key concept of the critical mass.

Fearful of German intentions with nuclear weapons and disturbed by the lack of American action, in 1939 Szilard persuaded Albert Einstein to write to President Roosevelt, urging him to initiate an American atomic weapons programme. He was rewarded for his pains by Major General Leslie Groves, leader of the Manhattan Project designing the atomic bomb, who in 1943, forced Szilard to sell his atomic energy patent rights to the U.S. government.

In like manner in 1942 the Russian nuclear physicist Georgy Nikolaevich Flerov noticed that articles on nuclear fission were no longer appearing in western journals from which he concluded that research on the subject had become secret, prompting him to write to Premier Joseph Stalin insisting that "we must build the uranium bomb without delay." Stalin took the advice and appointed Igor Vasilevich Kurchatov, director of the nuclear physics laboratory at the Physico-Technical Institute in Leningrad, to initiate work on Russia's bomb. Their first nuclear bomb was finally tested on 29 August 1949 near Semipalatinsk on the steppes of Kazakhstan. Flerov and Kurchatov both received the Soviet Union's highest award, the title of Hero of Socialist Labour and the Gold Star medal.

1932 Just when we thought we had an elegant and simple explanation of the structure of matter with three sub-atomic particles, a nucleus of protons and neutrons with electrons orbiting around it, along came quantum mechanics in the 1920's and shook the foundations of physics. But it didn't end there, the detection in 1932 by Anderson of the positron predicted by Dirac indicated the existence of a lower level of elementary particles which make up the basic building blocks of the sub-atomic particles. It initiated the discovery over the next 50 or more years of whole families of elementary particles including Leptons, Quarks, Bosons, Mesons and Baryons and each family may include a dozen or more fundamental particles many of which have corresponding anti-particles. Examples are Muons, Gluons, Pions, Kaons and the whimsically named Up, Down, Top, Bottom, Strange and Charm Quarks to name but a few. While this is interesting, nobody has yet found practical applications for these particles, but then Rutherford did not foresee any use for nuclear energy when he discovered nuclear radiation.

1932 G.W. Heise and W.A. Schumacher construct the first zinc air battery. High energy density primary cells, they were used to power Russia's Sputnik 1 in 1957.

1932 Sabine Schlecht and Hartmut Ackermann working in Germany invent the porous sintered pole plate which provides a larger effective electrode surface area and hence lower internal impedance and higher current capabilities bringing about major improvements to Nicad battery design.

1932 Nyquist proposes a method for determining the stability of feedback control systems. Known as the Nyquist stability theorem it was developed from the study of the behaviour of negative feedback amplifiers but it has universal applicability being applied to mechanical systems (position, speed, temperature, pressure controls) as well as electrical systems (voltage amplitude, frequency and phase controls) and even non physical models such as the national economy. It is used as a development tool to ensure stability of electronic control and protection circuits.

1932 Fibreglass, like glass, has been "invented" many times over. The first glass fibres of the type that we know today as fibreglass were discovered by accident by Dale Kleist working at Corning Glass. While attempting to weld two glass blocks together to form an airtight seal, a jet of compressed air unexpectedly hit a stream of the molten glass and created a shower of glass fibres indicating an easy method to create fibreglass. Fibreglass insulation had been patented in 1836 by Dubus-Bonnel, produced in volume by Player in 1870, patented again by Hammesfahr in 1880 and re-invented by Boys in 1887, however Russel Games Slayter of Owens-Corning was granted a patent for "Fiberglas" in1938.

The term 'fibreglass' is often used imprecisely for the composite material glass-reinforced plastic (GRP)

A fibreglass mat is an essential component used to absorb and immobilise the acid electrolyte in AGM Lead Acid batteries. Fibreglass composites are also used extensively for high power cell and battery casings.

1933 The "Dassler patent" recognized the oxygen cycle and recombination as fundamental principles of the sealed nickel-cadmium battery.

Research into improved nickel cadmium batteries by Schlecht, Ackermann and Dassler was driven by the need for light weight aircraft starting batteries.

1933 Walter Meissner and Robert Ochsenfeld discovered that when a superconducting material is cooled below its critical temperature magnetic fields are excluded or repelled from the material. This phenomenon of repulsion was discovered by Faraday and is known as diamagnetism. The low temperature effect is today often referred to as the "Meissner effect".

1933 Reginald O. Gibson and Eric William Fawcett, ICI chemists produced Polyethylene a polymer of ethylene gas. Like many chemical developments it was discovered by accident, this time while reacting ethylene and benzaldehyde at high pressure. Now used extensively in the electrical industry as an Insulator ICI gave it the name Polythene.

1933 Radio pioneer Armstrong patented Frequency Modulation (FM radio) as a way of reducing interference on radio transmissions. Since most electrical noise produces amplitude variations in the signal, Armstrong's system involved varying the frequency of the radio carrier wave (rather than the amplitude as in AM radio) in synchronism with the amplitude of the voice signal. By clipping the noisy signal the noise can be eliminated. The idea which revolutionised radio reception was at first rejected then stolen by his old friend David Sarnoff the founder and CEO of RCA in which Armstrong was a major shareholder.

Armstrong had previously fought a legal battle all the way to the supreme court over his 1912 invention of the regenerative radio receiver which amplified weak radio signals by feeding them back through a triode amplifier valve (tube). However in 1920 when the value of Armstrong's invention became known, Lee De Forest claimed ownership of the regeneration principle because it used his audion. Unfortunately after 12 years of litigation, the supreme court, not familiar at that time with such technical distinctions, found in De Forest's favour.

Like Farnsworth before him, Armstrong suffered at the hands of RCA. Short of funds and faced with more years of costly and heartbreaking litigation against former friends over his FM patents, in January 1954 Armstrong put on his hat, his overcoat and his gloves, stepped onto the ledge of his 13th floor apartment building in New York City and plunged to his death. His wife who had contributed to Armstrong's depression by refusing to help fund his litigation against RCA, continued it herself and eventually won.

1933 US patent awarded for flexible printed circuits made by Erwin E. Franz by screen-printing or stenciling a paste loaded with carbon filler onto cellophane, followed by a copper electroplating step to reduce the resistance. He also proposed using flexible folding circuits for windings in transformers.

1934 Lead acid batteries with gelled sealed cells were first manufactured by Elektrotechnische Fabrik Sonneberg in Germany.

1934 Invention of the transformer-clamp by Chauvin Arnoux, the very first current measuring clamp.

1935 The first practical Radar (RAdio Detection And Ranging) system was produced by the Scottish physicist Robert Alexander Watson-Watt a direct descendent of James Watt the pioneer of the steam engine. As fears of an impending war grew, he had been tasked by the Air Ministry to come up with a radio death ray to disable enemy aircraft, however he informed them it was not possible and proposed instead the system we now call Radar for detecting the presence of aircraft before they came into sight. This was accomplished by sending out powerful radio pulses and detecting their return after reflection by the aircraft and computing the distance from the time it took the pulses to return. Large directional antennas were used to concentrate the signals and provide an indication of the bearing of the target. Being a two way system, one of the major problems he had to overcome was to get very sensitive receivers to work in close proximity to very high power transmitters without being swamped. Watson-Watt received a knighthood in recognition of his achievements.

Ironically, after the war, Watson-Watt was amongst the first unsuspecting drivers to be caught in a Radar speed trap.

1935 German physicist Oscar Ernst Heil, working at Berlin University was granted a British patent for "Improvements in or relating to electrical amplifiers and other control arrangements and devices". His design was essentially an insulated gate field effect transistor (IGFET). Using semiconducting materials such as Tellurium, Iodine, Cuprous oxide or Vanadium pentoxide to form a resistor between two terminals, he applied a voltage across the device. By means of a third control terminal he created an electrostatic field across the device at right angles to the current and by varying the voltage on this control terminal he was able to vary the resistance of the semiconductor and thus modulate the current through an external circuit.

Heil's transistor was never developed into a practical product. Semiconducting materials of sufficient purity were not available at the time and in the period leading up to and during World War II the scientific communities of whomever he happened to be working for had other priorities.

Heil however had other interests which benefited from the new focus on research applicable to military applications. He had married Agnessa Arsenjeva a Russian physicist while working in Russia. In 1935, the same year that he was granted the patent for his semiconductor amplifying device, together with his wife he published in Zeitschrift fur Physik, a paper on velocity modulation of electron beams entitled: "A New Method for Producing Short, Undamped Electromagnetic Waves of High Intensity" which outlined the fundamental working principles of the klystron tube, a high power microwave oscillator, used to provide the transmitter power in the newly developed radar equipment. Leaving Arsenjeva in Russia, he later moved to the UK to continue development work on the klystron with Standard Telephones and Cables (STC), the UK arm of ITT. The day before England went to war with Germany Heil slipped out of the country returning to Germany to continue his work at Standard Electric Lorentz (SEL), ITT's German arm in Berlin. Heil's klystrons, known as "Heil's Generators", became key components in Germany's World War II radars.

After the war Heil's name appeared on an FBI list of Germans accused of war crimes. He was brought to the US by the military and worked at Wright Patterson Air Force Base. Subsequently he formed his own company and carried out intensive research the physiology of the human ear and sound generation by small animals which he applied to the design of sound transducers. His 1973 patent for the Heil Air Motion Transformer (AMT) made him well known to HiFi buffs.

1936 Carlton Ellis of DuPont was awarded a patent for polyester resin which can be combined with fibreglass to produce a composite.

The curing and manufacturing processes for polyester resin were further improved and refined by the Germans process. During World War II British intelligence agents stole secrets for the resin processes from Germany and turned them over to American firms. American Cyanamid produced the direct forerunner of today's polyester resin in 1942.

1937 The birth of digital technology. American mathematician Claude Elwood Shannon was the one of the first to realise the similarity between electric switching circuits, Boolean logic and binary arithmetic and the first to use these principles as a basis for information processing in his MIT thesis on Vannevar Bush's differential analyser. See also Zuse who developed these ideas independently. Shannon's work on digital technology formed a vital strand to his later work on Information theory.

Shannon, like Zuse, showed that logic devices which are commonly called gates may be implemented with mechanical switches, relays or valves (now transistors).

A computer can perform almost any logic or arithmetic operation using combinations of only three types of gates, called AND, OR, and NOT gates. If an "input" or an "output" is defined as a logic "1" and the absence of an input or output as a logic "0" then:

1937 Eccentric English engineer and visionary Alec Harley Reeves working at ITT in France invented pulse code modulation (PCM) to minimise the effect of noise on transmission systems. Although his system was used for top secret communications during World War II, it needed many more components than conventional analogue circuits and it was not until the availability of integrated circuits that the large scale deployment of digital PCM systems became economically viable.

Electrical noise can be a serious problem with all communications circuits. As a signal progresses down a communications channel it gets weaker and at the same time picks up electrical noise. Each time the signal is amplified to restore its level, the noise is amplified with the signal until the signal may eventually be swamped by the noise. Digital circuits avoid this problem by using a transmitter which samples the analogue signal at high speed (See Shannon above) and converts the amplitude of the signal into a series of pulses, coded so that the pattern of the pulses represents the amplitude of the signal. This process is known as quantising and may be used to derive a simple binary number or some more complex encrypted data code. Noise affects the pulsed or digital signal in exactly the same way distorting the signal, however weak signals are not amplified to restore the signal strength. Instead, using a technique first employed by Henry in 1831, the distorted or noisy pulses are simply used to trigger a new set of clean, high level pulses to replace the weak and dirty signal pulses. The original pulsed waveform is thus regenerated and the noise is left behind. At the receiving end the original analogue signal is reconstituted from the pulses. Because of their noise immunity and amenability to multiplexing and computer controlled data manipulation, digital circuits based on Reeves' work have now almost completely replaced analogue circuits even for the simplest of functions. Standard integrated circuits are available to carry out the analogue to digital (A to D) and digital to analogue (D to A) conversions.

Although a pacifist, Reeves developed a pinpoint bombing system during the war "to minimise civilian casualties". He worked on radar systems, multipexers, fibre optics and acoustic components and was awarded over 100 patents. He also experimented with the paranormal using Geiger counters, pendulums, and electronics in his research and believed he was in regular contact with the long dead Michael Faraday. He claimed to have played in the French Open tennis championships - which were indeed 'open' to anyone who wished to participate. Reeves dedicated his private life to community projects, helping others, encouraging youth and rehabilitating prisoners.

1937 English engineer Robert J. Dippy working in Watson-Watt's radar team conceived the radio navigation system using coordinated transmissions from three or more radio stations to pinpoint the location of a receiver. It relies on the fact that all the points where the time difference between radio signals from two different stations is constant form a hyperbola. The distance of the receiver from the transmitters (the locus of the hyperbola) can be calculated from the time differences from each transmitter. Signals from a second pair of stations determine another set of hyperbolas. The exact position of the receiver is determined by finding the point on the map where the two hyperbolas intersect. Dippy received a patent in 1942 for this invention which was implemented in the Gee navigation system used by the British Bomber Command in World War II. Dippy's principle of using intersecting radio beams was subsequently used in the LORAN navigation network and is used in the modern GPS (Global Positioning by Satellite) system in which the transmitters are located in orbiting satellites rather than in fixed ground based stations. Like computers, the early navigation systems were large and heavy and housed in equipment racks. Modern navigation receivers are hand held and battery powered.

After working as advisor on the development of LORAN in the USA, Dippy became a Divisional head of research in Australia's Defense Science and Technology Organisation.

1937 Printed circuits were demonstrated by London born British engineer with Hungarian parents John Adolphe Szabadi. In 1938 Szabadi changed his name to John Sargrove by which he is better known since Adolphe wasn't the most popular name in Britain at the time. His circuits were more like thick film integrated circuits than the printed circuit boards (PCBs) we know today. The system did not use etching as with modern PCBs. Instead, with the Sargrove method was an additive, process in which, not just the interconnecting circuit tracks but also the resistors, inductors, capacitors and other components were formed by spraying on to a pre-moulded bakelite panel.

1938 American engineer Hendrick Wade Bode building on Nyquist's work at Bell Labs employs magnitude and phase frequency response plots of a complex function to analyse closed-loop stability in electronic systems. This formed the basis of classical control theory used in the design of stable electronic and other control systems.

1938 Canadian inventor Al Gross invented the Walkiie-Talkie two way mobile radio which was quickly picked up by the military and widely used during the war. In 1948, he pioneered Citizens' Band (CB) radio and in 1949, he invented the telephone pager.

1938 Chemist Otto Hahn and physicist Fritz Strassman from Germany and Lise Meitner from Austria verified the possibility of releasing energy by the phenomenon of nuclear fission, the splitting of the atom, first demonstrated by Rutherford in 1917. They bombarded uranium with neutrons and the uranium nucleus split into two roughly equal halves forming Barium and Krypton with the emission of three neutrons and a large amount of energy, the basis for the chain reaction which gave rise to nuclear power and bombs. From her work in Germany, Meitner knew the nucleus of uranium-235 splits into two lighter nuclei when bombarded by a neutron and that the sum of the masses the particles derived from fission is not equal to the mass of the original nucleus. She speculated that release of energy would be a hundred million times greater than normally released in the chemical reaction between two atoms. She was however not present when Hahn and Strassmann verified this result experimentally since, being Jewish, she was forced to flee to Sweden to escape Nazi persecution when Austria was annexed by the Germans. The results were published by Hahn and Strassmann and Hahn alone was eventually awarded a Nobel Prize for chemistry for this work. Meitner was not credited in the report since Hahn feared the result would be rejected if it were known to be tainted by "Jewish science", - female Jewish science at that. The German nuclear weapons research programme during World War II was led by Heisenberg and neither Hahn, Strassmann nor Meitner were involved.

1938 Contrary to popular belief, non-stick Teflon was not a product of NASA's space program. It was discovered by accidentally in 1938 by DuPont chemist Dr. Roy J. Plunkett while investigating possible new refrigerants. His lab technician Jack Rebok found an apparently defective cylinder of tetrafluoroethylene gas. Although it was the same weight as full cylinders, no gas emerged when the valve was opened. Rebok suggested sawing it open to investigate and inside, Plunkett discovered that a frozen, compressed sample of tetrafluoroethylene gas had polymerised spontaneously into a white, waxy solid to form poly tetrafluoroethylene (PTFE).

PTFE has a high melting point, is inert to virtually all chemicals and is considered the most slippery material in existence. Now used as extensively an insulator or separator in a wide variety of batteries an other electrical equipment, it remained a military secret until after the end of World War II.

1938 German born American engineer Joseph G. Sola invented the Constant Voltage Transformer (CVT). Based on ferroresonant principles it has a capacitor connected across the secondary winding. The voltage on the secondary winding increases as the input voltage increases, however the corresponding increasing flux produces an increase in the leakage reactance of the secondary winding and this approaches a value which resonates with the capacitor connected across it. This causes an increased current which saturates the magnetic circuit thus limiting any further rises in output voltage due to increased input voltage. The output may not be a pure sine wave but usable outputs can be obtained with a swing of +/- 25% in the input voltage. Furthermore, the transformer will absorb short duration spikes and due to the energy storage in the resonant circuit the output will hold up for short power interruptions of half a cycle (10 milliseconds) or more, making it useful for UPS applications.

1938 Swiss born German physicist Walter H. Schottky explained the rectifying behaviour of a metal-semiconductor contact as dependent on a barrier layer at the surface of contact between the two materials which led to the development of practical Schottky diodes. He had been one of the first to point out the existence of electron "holes" in the valence-band structure of semiconductors.

1938 German civil engineer Konrad Zuse completed the world's first programmable digital computer, an electromechanical machine, which he called the Z1. Started in 1936, it was built in his parents' apartment and financed completely from his own private funds. It pioneered the use of binary arithmetic and contained almost all of the functions of a modern computer including control unit, memory, micro sequences and floating point arithmetic. Programs were input using holes punched into discarded 35-millimetre movie film rather than paper tape and data was input through a simple four decimal place keyboard. The calculation results were displayed on a panel of light-bulbs. The clock frequency was around one Hertz. Relays can be used to store data since the position of the contacts, closed or open, can be used to represent a one or a zero, but Zuse did not use this solution because relays were very expensive. Instead he devised a mechanical memory system for storing 16 X 22-bit binary numbers in which each memory cell could be addressed by the punched tape or film. For storing data it used small pins which could slide in slots in movable steel plates mounted between sheets of glass which held them together. The pins could move and connect the the plates and their position at either end of the slot was used to store the value 0 or 1. Individual memory units could be stacked on top of one another in a system of layers. In keeping with the German tradition of solid engineering Zuse claimed "These machines had the advantage of being made almost entirely of steel, which made them suitable for mass production".

Zuse was called up for military service in 1939 but was later released from active service, not to work on computers as might be expected, but to work as an aircraft engineer. He continued the development of his ideas in his spare time and, despite the shortages of materials, in 1941 he demonstrated his third machine imaginatively called the Z3. With limited backing from the DVL, the German Aeronautical Research Institute, this time he was able to use 2,600 relays, which were more reliable than his metal plates, to form the memory registers and the arithmetic unit. The memory capacity was increased to 64 words and the clock frequency was increased to 5.33 Hertz. The Z3 is the undisputed, first fully programmable practical working electronic digital computer. It was programmed using punched tape but because of size limitations of the memory, the Z3 did not store the program in the memory. Otherwise it used the basic architecture, patented by Zuse in 1936, and all the components of a modern computer, the concept for which Hungarian born American mathematician John von Neumann was later credited for defining in 1946.

After the success of the Z3 the government at last took notice of Zuse's work but when in 1942 he proposed a computer based on much faster electronic valves, it was rejected on the grounds that the Germans were so close to winning the War that further research effort would take too long and was therefore not necessary.

In the early aftermath of the war West Germany was prohibited from developing electronic equipment, materials were even scarcer than before and electrical power was only available intermittently. His latest computer the Z4 had also been damaged in the Berlin air raids but Zuse had managed to rescue it and after many difficulties he was eventually able to restart its development in Switzerland. Completed in 1950, the Z4 was the first computer in the world to be sold to a commercial customer, beating the Ferranti Mark I in the UK by five months and the UNIVAC I in the USA by ten months.

Between 1942 and 1946 Zuse also developed Plankalkül (German, "Plan Calculus") the world's first high level programming language but did not publish at the time. It included assignment statements, subroutines, conditional statements, iteration, floating point arithmetic, arrays, hierarchical record structures, assertions, exception handling, and other advanced features such as goal-directed execution. Intended as an engineering tool for performing calculations on structures, Zuse also used Plankalkül to write a program for playing chess. At that time the concept of software was unheard and surprisingly he did not start with machine oriented assembly language programming but immediately set out to develop the more complex user oriented language. Plankalkül was the first modern programming language at any level above manual toggle switching or raw machine code. It was finally published in 1972 and the first compiler for it was implemented in 2000 by the Free University of Berlin, five years after Zuse's death.

Until 1950 Zuse lived in complete isolation from the world outside Germany particularly during the war years when he remained in Berlin where his first three computers and his workshop were destroyed by allied bombing raids. He had little knowledge of computer developments elsewhere and his work was likewise almost unknown outside of Germany, although IBM obtained an option on his patents in 1946. He was not successful as a businessman and his company was sold to Siemens in 1967. Besides his engineering talents Zuse was also an accomplished artist who sold his paintings during his early years to fund his studies and at the end of the war sold woodcuts to American troops in order to buy food. In retirement he returned to painting as a hobby.

There have been many claimants to the title of The First Computer. For the record here are the dates when some other early programmable computers became fully operational:

Echoing Babbage's experience, with four out of the first eight modern computers, UK innovation once more was not translated into commercial success.

Computers have become essential tools in almost every aspect of engineering and business management and their modern counterparts, microprocessors are now key components in battery management systems.

1939 The German company I.G. Farbenindustrie filed a patent for polyepoxide (epoxy). Benefiting from German technology epoxy resins were made available to the consumer market almost four years later by an American manufacturer. They have very strong adhesive properties being one of the few materials which can make effective joints with metal. They are dimensionally stable and have similar expansion rates to metals. When combined with fibreglass they can produce an extremely strong composite materials, known as Glass Reinforced Epoxy (GRE) , strong enough for use as aircraft components.

Because of epoxy's chemical resistance and excellent electrical insulation properties, electrical parts such as batteries, relays, coils, and transformers are insulated with epoxy.

1940 John Turton Randall and Henry Albert Howard Boot working at Birmingham University developed the first practical cavity magnetron, a high power microwave transmitter valve (vacuum tube) which was an essential component in wartime Radar transmitters. It could generate 1000 times the power of any other existing microwave generator at the time. Now an essential component in microwave ovens.

1941 Silver oxide- Zinc (Mercury free) primary cells developed by French professor Henri André using cellophane as a semi permeable membrane separator which impeded the formation of dendrites which caused short circuits.

1941 Bell Labs researcher Russell S. Ohl discovered that semiconductors could be "doped" with small amounts of foreign atoms to create interesting new properties. He discovered the principles of the P-N junction (with some hints from Walter Brattain) and invented the first Silicon solar cell, a P-N junction that produced 0.5 volts when exposed to light. Ohl's invention of the semiconductor junction and his explanation of its working principles laid the foundations on which the invention of the transistor was based. Unfortunately, Ohl's essential contribution has almost been forgotten.

1941 American inventor B.N. Adams filed for a patent on the water activated battery. Working at home, he had developed the battery for military, marine and emergency us and he demonstrated it to the US Army and Navy. Unfortunately the US Army Signal Corps declared the invention to be unworkable. Nevertheless Adams was awarded a patent in 1943. At the height of World War II however the US Signal Corps decided the idea was indeed feasible after all and the government entered into procurement contracts with several battery making companies without informing Adams. He subsequently discovered in 1955 that his invention had been in use for some time by the US government who by then claimed the idea lacked novelty and was obvious and was therefore not patentable. In 1966 Adams sued the US government and the Supreme Court found in his favour and his 1943 patent was upheld.

1941 Patent granted to American inventor Harold Ransburg for the electrostatic spray coating process in which the paint is electrostatically charged and the surface to be painted is grounded. An idea first proposed by Nollet in 1750. Because of the electrostatic attraction between the positively charged paint and the grounded body the majority of the paint reaches its target resulting in major savings.

1941 Thick Film Circuits developed by Centralab division of Globe-Union Inc in the USA - An innovative use of screen printing technology patented in 1907. They used resistive inks and silver paste printed on ceramic substrates to form printed resistors, capacitors, links and other components in miniature circuits used in proximity fuses. Similar printing processes are used today to manufacture thin film batteries.

1942 Building on Chadwick's work, the first controlled, self-sustaining nuclear chain reaction was achieved by a team led by Italian Enrico Fermi in an atomic pile set up in a squash court at the University of Chicago. During nuclear fission, a fast-moving neutron splits an atom's nucleus, which results in the release of energy and additional neutrons. These ejected neutrons can split further nuclei, which release more neutrons to split yet more nuclei, and so on creating a self-sustaining chain reaction. If this chain reaction goes too fast, it becomes an atomic explosion, but under control it could produce a steady flow of energy. If the chain reaction starts with uranium, it also creates a byproduct, plutonium, a better fuel for a nuclear weapons. Fermi found that cadmium would absorb neutrons. If the chain reaction speeded up, cadmium rods could be inserted into the pile to slow the reaction down and could be removed to accelerate it again. If the cadmium control rods had failed or if they had got their calculations wrong, half of Chicago would have been blown up. As a precaution physicist Norman Hilberry stood poised with an axe during the start-up, ready to cut a rope and release more cadmium control rods that would stop the reaction in an emergency. If all else failed, a three-man "suicide squad" of physicists stood ready to drench the pile with cadmium sulfate.

This event marked the birth of the nuclear power industry and also the atom bomb.

1942 American chemist Harry Coover working on materials for optically clear gun sights accidentally discovered cyanoacrylate a fast acting transparent adhesive. It proved too sticky for the job in hand and its true potential was not realised until 1958 when it was marketed as Superglue. Now used extensively in industry for glueing together small sub-assemblies such as battery packs.

Superglue's ability to stick skin together was turned from a problem into a benefit during the Vietnam War saving the lives of countless soldiers when it was used in to seal battlefield wounds before the injured could be transported to a hospital.

1942 American chemists William Edward Hanford and Donald Fletcher Holmes working at du Pont de Nemours invented the process for making the multipurpose material polyurethane. Now extensively used as a foam insulating material in a wide range of applications.

1943 The printed circuit board was patented in the UK by Austrian born Jewish refugee Paul Eisler, the acknowledged father and publiciser of the PCB. Most

Battery and Energy Technologies

History of Batteries (and other things)

Heroes and Villains - A little light reading