298 Mr. Gassiot on the relation of Electrical Sf Chemical Actions 



nection with the earth, and consequently having the intensity 

 exalted to a maximum short of actual discharge. 



33. I am aware of the many forms the contact theory has 

 assumed since Volta first propounded it; nor. can we lose 

 sight of the many errors which his successors have committed 

 in attempting to follow out their favourite views of metallic 

 contact and electro-motive forces. I am indebted for much 

 information on this point to the kindness and industry of Mr. 

 C. V. Walker, who has occupied much time in procuring me 

 references to the researches of those electricians already al- 

 luded to, as also to a long list of others whose names adorn 

 the pages of science. I could easily have added to those I 

 have named, by referring to the experiments of many other 

 authors who consider that their favourite theory of contact has 

 been fully established. It is not, however, my object to advert 

 to these speculations: we have before us certain facts con- 

 nected with the action of the voltaic battery ; first contact^ or 

 successive juxtaposition, and simultaneously with it, effects of 

 tension] then the completion of the circuit, and simultaneously 

 with it, development of chemical action and current', but in all 

 these cases contact is first in order, developing tension. Bec- 

 querel describes it by stating, " When two bodies are in con- 

 tact the affinities commence exercising their action before com- 

 bination takes place." M. De la Rive, " The electricity of 

 tension developed by contact of heterogeneous bodies." Fa- 

 raday, "That the particles of the electrolyte are brought into 

 a polarized state, and raised to a certain degree of tension, 

 before discharge takes place:" but I am not aware that there 

 are any experimental facts to prove whether this tension in the 

 voltaic battery, which itself is of an opposite character at each 

 terminal, and, as we have seen, can be exalted so as to pro-* 

 duce discharges in the form of sparks for many weeks' con- 

 stant duration (16.), is due to the chemical constituents of the 

 battery, or to mere contact of dissimilar bodies, without refer- 

 ence to their chemical affinities. I was therefore most anxious 

 to see whether some experiment could not be devised, which 

 would test the action in a satisfactory manner, and for this 

 purpose I availed myself of an extended series of Grove's gas 

 battery, described by him in a paper already alluded to (23.)*. 

 34. The elements used in this form of the voltaic battery 

 consist of two gases and one metal; with fifty series charged 

 with oxygen and hydrogen, it is stated that the gold-leaf 

 electroscope was notably affected. The instrument used by 

 Mr. Grove, whose original experiments I had the pleasure of 

 witnessing in the laboratory of the London Institution, was 

 • Philosophical Transactions, 1843. 



