Mr. J. J. Waterston on some Electrical Experiments. 373 



if the B. D., when close to the top of the shade, is kept in posi- 

 tion for a few seconds, the leaves sink a little (showing a decre- 

 ment A of the inductive force acting on the electroscope, although 

 there is no decrement of the charge on B. D.) ; and on removing 

 it they shut and then open with the opposite electricity, and 

 the extent of the opening corresponds to the decrement A, thus 

 showing that the top of the glass shade has been inductively 

 excited by B. D. But this excitement is evanescent, the leaves 

 subside in a few seconds. The explanation of such phenomena 

 that first presents itself is, that the outer surface of the shade is 

 a partial conductor ; but if this were the case, how is it that on 

 bringing theB.D. into contact with the glass shade it does not lose 

 charge, although its intensity is much greater than the induced 

 excitement which so quickly passes away ? The lesser intensity 

 cannot be conducted more easily than the greater. Insulating 

 the glass shade, by resting it upon sulphur, makes no difference. 

 It appears to be a constrained local polarization, in which the 

 work-equivalent of the charge is partially expended in effecting 

 a change of molecular condition ; but there is no separation of 

 the electricities accompanied with conduction, as takes place on 

 a truly conducting metallic surface subject to the inductive in- 

 fluence of a charged body. 



Faraday's view of static induction has led him to give a defi- 

 nition of disruptive discharge, which I think is also unfortunate as 

 tending to close further inquiry in the very direction most likely 

 to lead to important discovery in the dynamical conditions affect- 

 ing the relations of molecules to the higher potential medium. 

 In recent educational works it is mentioned, not as a conjecture, 

 but as an established fact, that " the particles of the intervening 

 dielectric are brought up to a highly polarized state, until at 

 length the tension on one particle rising higher than the rest, 

 and exceeding that which it can sustain, it breaks down ; the 

 balance of induction is thus destroyed, and the discharge is com- 

 pleted in the line of least resistance." In my tenth and eleventh 

 experiments it may be remarked that the disruption that accom- 

 panies discharge is like what is caused by mechanical impulse 

 of matter pressing with sudden and short-lived force. If this 

 idea is kept in view and arrangements made in accordance with 

 it, experiments on the discharge of high-tension electricity would, 

 I believe, assume a new and exciting interest, and lead; if well 

 planned, to a deeper insight into the arrangement of force in 

 nature than we could otherwise hope for. 

 I remain, Gentlemen, 



Your obedient Servant, 



John James Waterston. 



Edinburgh, March 20, 1865. 



