34 Mr. M. Donovan on the supposed Identity of the Agent 



term current being used in a sense which I conceive cannot be 

 reconciled with the laws of electricity. 



Without examining these opinions separately and in any par- 

 ticular order, it will answer the purpose and save trouble to make 

 mixed observations calculated to bring what I conceive to be 

 their defects under observation. 



TMiatever difference of opinion may exist relative to the nature 

 of positive and negative electricity, whether they are states of 

 one fluid, or two distinct fluids, or vibrations of a peculiar fluid 

 or of matter, I believe it is a position universally agreed to 

 amongst electricians, that when equal to each other and at liberty 

 to act, they mutually neutralize and destroy each other's proper- 

 ties. To quote authorities would be to enumerate all the authors 

 who have written on the subject, I shall merely quote the ex- 

 pression of the fact as stated by Sir H. Davy : — "In all cases of 

 electrical action, the two electrical states are always coincident, 

 either in different parts of the same body, or in two bodies, and 

 they are always equal and capable of neutralizing each other. 

 If a connexion be made by a wire between the positive and ne- 

 gative conductors of the electrical machine daring the time of its 

 action, all electrical effects cease*." Instances without number 

 might be adduced in support of the truth of this position ; but 

 to proceed with them would be to prove what nobody doubts. 

 Universall}', if the two electricities be equal in quantity and in- 

 tensity and are at perfect liberty to neutralize each other, all 

 symptoms of both disappear, a condition of absolute qiiiescence 

 results, that of equilibriinoi, in which all bodies naturally exist, 

 is induced ; and in this state they manifest no electrical pro- 

 perties. 



The poles of a voltaic series being in the positive and negative 

 states, conform to the general law. When the poles are uncon- 

 nected, they manifest their electrical condition to a gold-leaf 

 electrometer ; but as soon as they are connected by a good con- 

 ductor, the positive and negative states and all symptoms of 

 electricity vanish. 



This is a fact, which, so far as electrical appearances are con- 

 cerned, is universally admitted ; yet it may not be without use 

 to advert to the very striking exemplification of it lately given 

 by Mr. Gassiot, on a scale of expense and magnificence rarely 

 equalled by an indi\'idual. With a water battery consisting of 

 3520 pairs of copper and zinc cylinders, each pair being placed 

 in a separate glass vessel well varnished, Mr. Gassiot made the 

 following obscnation : — " The tension was so great that the gold 

 leaves of an electroscope diverged when that instrument was 



* Elements of Chemical Philosophy, p. 132. The thickness of the wire 

 must be proportional to the quantity to be conducted. 



