<P> The first appearance of the term electromagnetism on the other hand comes from an earlier date: 1641 . Magnes, by the Jesuit luminary Athanasius Kircher, carries on page 640 the provocative chapter - heading: "Elektro - magnetismos i.e. On the Magnetism of amber, or electrical attractions and their causes" (ηλεκτρο - μαγνητισμος id est sive De Magnetismo electri, seu electricis attractionibus earumque causis). </P> <P> The electric machine was subsequently improved by Francis Hauksbee, his student Litzendorf, and by Prof. Georg Matthias Bose, about 1750 . Litzendorf, researching for Christian August Hausen, substituted a glass ball for the sulphur ball of Guericke . Bose was the first to employ the "prime conductor" in such machines, this consisting of an iron rod held in the hand of a person whose body was insulated by standing on a block of resin . Ingenhousz, during 1746, invented electric machines made of plate glass . Experiments with the electric machine were largely aided by the discovery of the property of a glass plate, when coated on both sides with tinfoil, of accumulating a charge of electricity when connected with a source of electromotive force . The electric machine was soon further improved by Andrew Gordon, a Scotsman, Professor at Erfurt, who substituted a glass cylinder in place of a glass globe; and by Giessing of Leipzig who added a "rubber" consisting of a cushion of woollen material . The collector, consisting of a series of metal points, was added to the machine by Benjamin Wilson about 1746, and in 1762, John Canton of England (also the inventor of the first pith - ball electroscope) improved the efficiency of electric machines by sprinkling an amalgam of tin over the surface of the rubber . </P> <P> In 1729, Stephen Gray conducted a series of experiments that demonstrated the difference between conductors and non-conductors (insulators), showing amongst other things that a metal wire and even pack thread conducted electricity, whereas silk did not . In one of his experiments he sent an electric current through 800 feet of hempen thread which was suspended at intervals by loops of silk thread . When he tried to conduct the same experiment substituting the silk for finely spun brass wire, he found that the electric current was no longer carried throughout the hemp cord, but instead seemed to vanish into the brass wire . From this experiment he classified substances into two categories: "electrics" like glass, resin and silk and "non-electrics" like metal and water . "Non-electrics" conducted charges while "electrics" held the charge . </P> <P> Intrigued by Gray's results, in 1732, C.F. du Fay began to conduct several experiments . In his first experiment, Du Fay concluded that all objects except metals, animals, and liquids could be electrified by rubbing and that metals, animals and liquids could be electrified by means of an electric machine, thus discrediting Gray's "electrics" and "non-electrics" classification of substances . </P>

The earliest ideas of charge were the result of experiments by