xliv 



TIIK PKOGUESS OF 



n:is excited in it by friction \,itli tlie hands. 

 A \\ire was hung from the other end of the gun 

 barrel, \\liich dipped into .1 beer glass, full of 

 water, and held in the hands of one of the gentle- 

 men. After the globe had been driven for some 

 time, the gentleman \\lio held the beer glass ap- 

 plied his finger to the gun barrel to draw a spark 

 from it. The consequence was a shock, differing 

 in violence according to the length of time that 

 the globe had been turned. Such was the origin 

 of the famous Leyden phial experiment, \vliicli 

 it first excited universal astonishment and terror; 

 but was very soon exhibited in London and 

 Paris, and indeed in all the large cities of 

 Kurope, and drew crowds of spectators to witness 

 the phenomena, and to feel the shock. 



It was found that this shock could be given at 

 once to any number of persons, provided they 

 laid hold of each other's hands, and that every 

 person (how great soever the number might be) 

 received the shock at the same instant of time. 

 Advantage was taken of this shock to determine 

 the rate at which electricity moves. Dr Watson 

 made an electric discharge pass through 12,276 

 feet of wire. One gentleman held a charged 

 Leyden jar in one hand, and the extremity of 

 the wire in the other. Another gentleman held 

 the other extremity of the wire in one hand, and 

 with the other brought a short iron rod in con- 

 tact with the knob of the Leyden jar. The con- 

 sequence was a discharge of electricity, and both 

 the gentlemen received the charge at the same 

 instant of time. So that electricity passes over 

 a circuit of two miles instantaneously, or at least 

 in an interval of time too short to be noticed. 

 Indeed, in one of Dr Watson's experiments, the 

 circuit through which the electricity passed was 

 nearly six miles in length, yet no sensible inter- 

 val of time was taken up by it in this long extent 

 through which it had to pass. 



The first successful attempt to explain the 

 phenomena of electricity was made by Dr Frank- 

 lin, in a series of letters addressed to Peter 

 Colinson, Esq., from Philadelphia in America. 

 These letters had been offered to the Royal 

 Society, but were refused a place in the transac- 

 tions of that learned body. When they made 

 their appearance in 1754 they drew universal 

 attention, were almost immediately translated 

 into all the European languages ; and as if this 

 had not been sufficient, they were ushered into 

 the world in a Latin dress. Dr Franklin con- 

 ceived that only one electric fluid existed, and 

 that all the phenomena of electricity were occa- 

 sioned either by its accumulation in bodies in 

 more than its natural quantity, or by its being 

 withdrawn from bodies, so as to leave in them 

 less than the usual quantity. When a body con- 

 tains its natural quantity of electricity, it exhibits 



no electrical phenomena whatever. \\ lien elec- 

 tricity accumulates, the phenomena of the vitreouf 

 electricity of Dufay are exhibited. When elec- 

 tricity is deficient, we perceive in it the pheno- 

 mena of the resinous electricity of Dufay. Be- 

 sides this theory, which probably occasioned his 

 immediate celebrity, electricity is indebted to 

 him for three capital discoveries. 1. Electricity 

 is dissipated at a great rate by points, so that it 

 is impossible to accumulate it in pointed bodies. 



2. The second and greatest discovery of Dr 

 Franklin was, that lightning and thunder are 

 occasioned by the accumulation of electricity in 

 the atmosphere'; or, in other words, that lightning 

 is the same thing with electricity. The analogy 

 between lightning and electricity had been point- 

 ed out already by the Abbe Nollet, and was 

 generally admitted; but Dr Franklin having 

 discovered the power of pointed bodies to dis- 

 charge electricity at a distance, first thought of 

 employing that method to render atmospheric 

 electricity sensible. Not having in America the 

 requisite means for such an experiment, he re- 

 quested the electricians in Europe to turn their 

 attention to it. The first person who attended 

 to the suggestion was 31. D'Abelard, who con- 

 structed an apparatus for the purpose at Marly 

 la "Ville, about six leagues from Paris. It con- 

 sisted of an iron rod forty feet long, the lower 

 extremity of which was brought into a centry- 

 box, where rain could not enter ; while, on the 

 outside it was fastened to three wooden posts 

 by silken strings defended from rain. 31. 

 D'Abelard was obliged to leave home ; but in his 

 absence he intrusted his machine to one Coisier, 

 a joiner, who had served fourteen years among 

 the dragoons, and on whose courage and under- 

 standing he could depend. This artisan had all 

 the requisite instructions given him, and he was 

 desired to call some of his neighbours, particular- 

 ly the curate of the parish, whenever there should 

 be any appearance of a thunder storm. On 

 Wednesday the 10th of May, 1752, between two 

 and three in the afternoon, Coisier heard a 

 pretty loud clap of thunder. Immediately he 

 ran to the machine, taking with him a phial fur- 

 nished with a brass wire ; and presenting the 

 wire to the end of the rod, a small spark issued 

 from it with a snap, like that of a spark from an 

 electrified conductor. Stronger sparks uere 

 afterwards drawn in the presence of the curate 

 and a number of other people. The curate's 

 account of them was that they were of a blue 

 colour, an inch and a half in length, and smelled 

 strongly of sulphur. In taking them Coisier re- 

 ceived a stroke on his arm, a little below the 

 elbow. 



Dr Franklin, after having published his views 

 on the subject, was waiting for the erection of a 



