328 



LESSONS IN ELECTRICITY. 



electroscope E. The effect is small, but 

 distinct. 



The greatest experiment with hollow 

 conductors was made by Faraday, who 

 placed himself in a cubical chamber built 

 of laths and covered with paper and wire 

 gauze. It was suspended by silk ropes. 

 Within this chamber he could not detect 

 tho slightest sign of electricity, however 

 delicate his electroscope, and however 

 strongly the sides of the chamber might 

 t>e electrified. 



29. Physiological Effects of the Elec- 

 tric Discharge. 



The physiological effect of the electric 

 shock lias been studied in various ways. 

 Graham caused a number of persons to 

 lay hold of the same metal plate, which 

 was connected with the outer coating of 

 a charged Leyden jar, and also to lay 

 hold of a rod by which the jar was dis- 

 charged. The shock divided itself 

 equally among them. 



The Abbe Nollet formed a lino of one 

 hundred and eighty guardsmen, and sent 

 the discharge through them all. He also 

 killed sparrows and fishes by the shock. 

 The analogy of these effects with those 

 produced by thunder and lightning could 

 not escape attention, nor fail to stimulate 

 inquiry. 



Indeed, as experimental knowledge in- 

 creased, men's thoughts became more def- 

 inite and exact as regards the relation of 

 electrical effects to thunder and lightning. 

 The Abbe Nollet thus quaintly expresses 

 himself : " If any one should take upon 

 him to prove, from a well-connected 

 comparison of phenomena, that thunder 

 is, in the hands of Nature, what electric- 

 ity is in ours, and that tho wonders 

 which we now exhibit at our pleasure are 

 little imitations of those great effects 

 which frighten us ; I avow that this idea, 

 if it was well supported, would give me 

 a great deal of pleasure.' lie then 

 points out the analogies between both, 

 and continues thus : " All those points 

 of analogy, which I have been some time 

 meditating, begin to make me believe 

 that one might, by taking electricity as 

 the model, form to one's self in relation to 

 thunder and lightning, more perfect and 

 more probable ideas than what have been 

 -offered hitherto."* 



* Priestley's " Ilistorvof Electricity," pp. 

 151-52. 



These views were prcralent at tho time 

 now referred to, and o.ut of them grew 

 the experimental proof by tne great 

 physical philosopher, Franklin, of the 

 substantial identity of the lightning Gash 

 and the electric spark. 



Franklin was twice struck senseless by 

 the electric shock. lie afterwards sent 

 the discharge of two large jars through 

 six robust men ; they fell to the ground 

 and got up again without knowing what 

 had happened ; they neither heard nor 

 felt the discharge. Priestley, who made 

 many valuable contributions to elec- 

 tricity, received the charge of two jars, 

 but did not find it painful. 



This experience agrees with mine. 

 Some timo ago I stood in this room with 

 a charged battery of fifteen large Leyden 

 jars beside me. Through some awkward- 

 ness on my part I touched the wire lead- 

 ing from the battery, and the discharge 

 went through me. Fur a sensible inter- 

 val life was absolutely blotted out, but 

 there was no trace of pain. After a life- 

 tie time consciousness returned ; I saw 

 confusedly both the audience and the ap- 

 paratus, arid concluded from this, and 

 from my own condition, that I had re- 

 ceived the discharge. To prevent the 

 audience from being alarmed, I made 

 the remark that it had often been my de- 

 sire to receive such a shock accident- 

 ally, and that my wish had at length 

 been fulfilled. But though th intellect- 

 ual consciousness of my position return- 

 ed with exceeding rapidity, it was not so 

 with the optical consciousness. For, 

 while making the foregoing remark, my 

 body presented to my eyes the appear- 

 ance of a number of separate pieces. 

 The arms, for example, were detached 

 from the trunk and suspended in the air. 

 In fact, memory and the power of rea- 

 soning appeared to be complete, long be- 

 fore the restoration of the optic nerve to 

 healthy action. 



This may be regarded as an experi- 

 mental proof that people killed by light- 

 ning suffer no pain. 



80. Atmospheric Electricity. 



The air at all times can bo proved to 

 be a reservoir of electricity, which un- 

 dergoes periodic variation. We have 

 seen that ingenious men began soon to 

 suspect u common on^is. for the crack- 



