Contact Theory of Galvanisiyi. 377 



1. That it is not solely the contact of metals, or, generally, 

 solid bodies with one another, which is capable of developing 

 electricity. 



2. That the excitation of electricity caused by the fluids, 

 whether from their mutual contact, or from contact with solid 

 bodies, does not follow exactly the same laws as that which 

 arises from the mutual contact of solid bodies. The first is 

 merely a generalization of the theory of contact, already made 

 by Yolta; the latter is no objection against it, since we do 

 not know what influence the aggregate state has upon the still 

 obscure process of the development of electricity. Expe- 

 rience certainly shows, undoubtedly, that fluids are not ame- 

 nable to the same law of galvanic tension as solid bodies, or that 

 if such is the case, secondary consequences resulting from the 

 mobility of the particles, changes of metallic surface, or other 

 circumstances, modify the result. The latter is my opinion, 

 of which I have given a general explanation (although with- 

 out paying sufiicient attention to the changes of metals) in Blot's 

 Lehrbuch {Precis), Part III. p. 321. 372., and which, up to the 

 present time, I have found no inclination to abandon. Then, 

 almost all the facts recently published by Faraday appear to 

 me to be for this reason much more important than they are 

 represented to be by his own statements. Be this, however, 

 as it may, (for I will force this view on no one) experiments in 

 which we see electricity originate even without the contact of 

 solid bodies, or so that this is of no influence, and, at the same 

 time, thus observe the fluids acting a part different from 

 that of solid bodies, cannot give proofs against the theory of 

 contact. We must also consider, in this point of view, the 

 following experiment by De la Rive, which 1 will relate, to- 

 gether with my own observations x'especting it. It is found, 

 with some little variation, in the Recherches, p. 62. 



" To each end of a wooden cylinder, of from 10 to J 2 cen- 

 timetres in length, and 1 to 2 centimetres in diameter, I fast- 

 ened a plate of zinc, which terminated outwards in a soldered 

 brass point; taking at present the brass point of the one plate 

 in my hand, 1 touched the condenser (also of brass) with the 

 brass point of the other. According to the theory of contact, 

 I ought to have obtained no sign of electrical activity, both 

 the zinc and the brass plates lying opposite to each other, 

 and being united by an insulated piece of wood which perform- 

 ed the office of conductor between both plates. Because, how- 

 ever, the one end of the wooden cylinder was moister than the 

 other, I obtained signs of electricity, the nature of which bore 

 a constant ratio to the chemical action, which was excited by 

 the contact of the carefully brightened zinc with the moist 



