ELECTRICITY. 



109 



things." It is the basis of the only theory of electricity which has been found 

 sullicient to explain all the phenomena of the science, and with the subsequent 

 hypothesis of Symmer, and the laws of attraction developed by the researches 

 of Coulomb, it has brought the most subtle and incontrollable of all physical 

 agents under the subjection of the rigorous canons of mathematical calcula- 

 tion. 



A new question now arose respecting any body which has been rendered 

 electrical, whether by immediate excitation, or by contact with another body 

 already excited. It was not enough to ascertain that it was electrified ; but it 

 was necessary to know with which of the two kinds of electricity it was in- 

 vested. The test of this proposed by Dufaye was the same which has ever 

 since his time been adhered to. He electrified a light substance freely sus- 

 pended with a known species of electricity ; say, for example, with resinous 

 electricity. If this substance was repelled on bringing it near another electri- 

 fied body, then the electricity of that body was known to be resinous ; but if, 

 on the contrary, it was attracted, then the electricity of the other body was 

 known to be vitreous. 



Dr. Desaguliers, whose works in other parts of physical science are well 

 known, devoted some attention to electricity from the close of the labors of 

 Grey till the year 1742, but the researches of this philosopher contributed 

 nothing to the extension of the science. He methodized the elements which 

 had already accumulated, and improved in some important instances the no- 

 menclature. He denominated all substances in which electricity may be ex- 

 cited electrics per se, and defined in a distinct manner their characters. He 

 also first applied the term conductor to bodies which freely transmitted electrici- 

 ty, and showed that animal substances owed this property to the fluids which 

 they contain. He however failed to discover that moisture was the conducting 

 agent in many other bodies which at that time were used to propagate elec- 

 tricity to a distance. 



The subject of electricity now began to attract the attention of the Germans, 

 and the first consequence was considerable improvement in the power and effi- 

 ciency of electrical apparatus. The globe of glass revolving on a horizontal 

 axis, which had originated with Hawkesbee, but had, ever since that time, 

 greatly to the detriment of the science, been abandoned in favor of the glass 

 tube, was now resumed by Professor Boze of Wittemburg, who added, for the 

 first time, the prime conductor to the machine. This conductor consisted of an 

 oblong cylinder, or tube, of iron or tin. It was at first supported by a man, 

 who was insulated by standing on cakes of rosin ; but it was subsequently sus- 

 pended by silken cords. 



The method of exciting the globe or tube hitherto generally practised, and, 

 indeed, long afterward persevered in, was to rub them with the hand, taking 

 care that it was dry -and warm. Winkler, a professor in the university of 

 Leipsic, substituted the more convenient expedient of a cushion fixed in con- 

 tact with the globe, and gently pressed upon its surface by springs, or any 

 similar means. Gordon, a Scottish Benedictine monk, who was professor of 

 philosophy at Erfurt, abandoned the use of the globe, and substituted for it a 

 cylinder of glass, having its geometrical axis horizontal, and supported on 

 pivots so as to revolve on that axis. The cylinders he used were eight inches 

 long, and four inches in diameter. Thus the electrical machine assumed a 

 form very nearly identical with the cylindrical machines of the present day. 



The effects produced by these improved and powerful apparatus are related 

 to have been extraordinary. Various inflammable substances, such as spirits, 

 heated oil, pitch, and wax, were fired. Appearances of electrical light issuing 

 from points, and the experiment since known as the electrical bells, were the 



