11 4 



R L E C T R I C I T V. 



hair, silk, linen, woollen, paper, leather, firwood shn- 

 parchment, and gold beater's le.-tf in which 



... : .;, i ecame c 1 . , in. .1 \\ I;, n i \>- ;> i u iih 



: !. 1 le found that the silk nnd the liiu-n, and 

 '...|-!\ a piece of white pressing p:i|KT, i, iclded ;i 

 IV'ht when rubbed in the dark, mid the- tir>t of : 

 bodies emitted .it the same time :. crackling ' 

 From .It-. Mr < >ray was ltd to the division of 



all substances i:. .-, or tho-r which can IT < \- 



citcd i , and nim-eleclrics, or those which can- 



ed tiy friction. 



In l-'t.! iruary 1729, wln-n Mr ( ',ray was makin 

 periiner.t- with a i>bss tuln- corked .a one end. It 

 surpri.-i'd to find t!iut n feather was attracted and re- 

 pelled by the cork. He then !y fixed to the 



.1 tube a stick of fir, a brass wire, n pack-thread, 

 iron, gold, silver, copjHr, tin, *!<:;.-. bricks, wood, ani- 



:.nil water, and louini in e\er\ case, llnl Uicclec- 



rtue was communicated most powerfully to llieir 

 ftirtlier extremity. In this w;,y he tried long < 

 and reed* aliove '20 and 30 feet long, anil obtained the 

 Mine result. In attempting to convey tire electric, vir- 

 tue to a great distance horizontally, Mr Gray and hi* 

 friend Mr Wheeler, found it necessary to suspend their 

 horizontal line by little vertical lines, to prevent it from 

 binding. When those supporting lines were silk, the 

 electricity was communicated as formerly to the end of 



l^i, 117, and 76.5 feet long ; but the silk hap- 

 pening to break, and n piece of brass wire being sub- 

 stituted on account of its greater strength, they were 

 astonished to find that the electric virtue was no longer 

 communicated, having been all carried off by the brass 

 wire. In this way Mr Gray was led to the important 

 general law, that non-electrics, such as the metals, were 

 conductors of electricity, while electrics, such as glass, 

 silk, hair, and rosin, were non-conductors, and may be 

 employed for the purpose of insulating conductors, in 

 order to convey electricity to any distance. In pur- 

 suing these enquiries, Mr Gray next found that he 

 could convey the electric energy from the excited tulxj 

 to a thread and to a rod without bringing them ir.to 

 contact with the tube, and that a bubble of v ater, wa- 

 ter itself, and all animal bodies, were likewise conduc- 

 tors of electricity. 



Mr Gray's attention was next directed to the electrical 

 qualities of rosin, gum lac, shell lac, Ix-es wax. sulphur, 

 iind pitch. I lav ing melted in a spherical iron l..<i<!le all 



-ubstances except the sulphur, either separately, 

 or when two or three of them were compounded, he 

 discovered, that when they were taken out of the 

 laddie, and had their spherical surfaces hardened, they 

 would not attract light bodies until they came down to 

 a certain temperature. The attractive power being then 

 developed, increased during t'le operation of cooling, and 

 became very considerable when the bodies were cold. 

 Having wrapped the smallest of these bo. lies in white 

 paper, ami the larger ones in white flannel, or in black 

 wonted, he enclosed thi m in a large fir box, and he found 

 that after 30 days, they were as powerfully attractive 

 -- on the first or teoonu day; and that at the.- end of four 

 months, (the time when he was writing,) they still re- 

 tained their power. He always melted the sulphur in 

 a glass vessel, and he once obtained a large and curious 

 one of stone sulphur, which was made in a wineglass, 

 .-ind which he had always kept covered by the inc- 

 When tbegUH wat removed, the cone at- 



i to it lw>dies as powerfully as the other piece 

 of sulphur which was preserved covered in the box. 

 The glass iuclf exhibited an attractive power m fair 



weather, but it was inferior to that of the sulphur, Jli 

 wliich . ^- *~Y~*"' 



sulphur which he h.,d kept for mo- milv one- 



tenth of the attr.ictiv < force of the cone. Mr Gray, in 



ith Mr Wheeler, <i' .-ibnut th. 



of August t a thnad susjiended in 



d by the ri ceiver ud. or b 



. d tulx-, atler the air ; .-tnii Mr 



Wheeler after\\.ird.s obi: : i :ne result when the 



attraction passed through . -ted. 



'. in this can er of <hs- DiswvTTif* 

 M. Dufav > 



and M I lis A ' lx 173A 



experiments were published in six long memoir*. LIM-I ted 

 among those of the Ac.i.iemv < and 



and entitle him to !>, 



wi'.l.-ly enlarged thft boundar: ' si.-iciicc. 



He discovered that all bodies excepting metals, fluids, 

 and sulphur, which ened by heat or dissolved 



by water, could be n 

 ;ind then rubbing them with any Kind of cloth. 



: IwKiies requiring i: 



d in repe.-itiiig Mi 



tie found that nil i ..! or fluid, 



were capable of t on 



r dry or slightly warmed, Hefound 



at the electric virtue was m> .uni- 



cated by pack-thread when it v .!, and in tliis 



way he conveyed it along a u,t long. 



M. Dufay had al--o the good fortune to be the fir-t 



eel the electric spark from a living bodv > 

 suspended on silk line-.: and lie has described the sen- 

 sations which he experienced when electrified in mi in- 

 sulated position. The most important di-coveri' 

 M. Dnliiy were two general laws, which enabled him to 



| a great number of obscure and inexplicable facts. 

 He discovered, 1. That electric bodies attract all tiio-e. 

 that are not so, communicate electricity to them, and 

 then repel them as soon as they And, 



'2. That there .".re two distinct kinds of electricity, very 

 I'.iiii-rcnt from one another, one of which he cal- 

 ami the other ic*i:io't.t electricity. The vilrt'oiis elec- 

 tricity is exhibited by Y(/.v. ro /. cri/xtt.l, jiri'dom- A. 

 hair (if ii/iiina/x, w<il, and many other boi:i 

 the resinout electricity is possessed by 

 ! I'.c, silk, tlircati . ind a f;reat. numb 



other substances. A body possessing vitieous elec- 

 tricity repels all bodies having vitreous electricity, and 

 attracts all that have resinous electricity, ami c 

 or in other words, bodies having the same electric 

 repel each other, and those which have contrary > 

 tricities attract each other. He likewise found, that 

 Communicated electricity was always of the same kind 

 ys that of the bodv which communicated it; and that a 

 tube full of condensed air was not capable of being 

 excited. 



oon as Mr Gray was made acquainted with M. F U rt!u-r - 

 Dufay 's experiments, he repeated the greater part of jxrii 

 them, and was led to some new and intc i -ults. Mrliray. 



M Dufay had observed, that a piece of iron drew 

 from the human body, when insulated bv 

 from which Mr Gray concluded, that the - 



would be produced if the metal and the human 

 body changed places. lie therefore suspended the po- 

 ker, the tongs, \c. before an excited i Vctric. and found 

 that tliey (jave sp.irks exactly like the human body. 

 Hence originated metallic conductors, which now form 

 essential parts of an electrifying machine. Mr Gray 

 likewise found, that knobs gave greater sparks than 



