488 M. Poggendorff on Galvanic Circuits composed of 



regard need be had to an isolated fact speaking apparently in 

 favour of the chemical theory, considering the numerous objec- 

 tions which may be urged against it. 



In general they may have contented themselves with this 

 otherwise perfectly correct position, that one metal, as soon as 

 it is in contact with two fluids, can no longer be regarded as a 

 single metal; so, for instance, that in Faraday^s experiment 

 that end of the zinc-bar which touched the sulphuric acid 

 would be positive towards that which was moistened by the 

 solution of the iodide of potassium. This at least is the opi- 

 nion which Pfaff advances in his Revision der Lehre vom 

 Galvano-Voliaismus^^. Pfaff is also, as far as I am aware, the 

 only philosopher on the continent who has hitherto publicly 

 discussed this experiment, without, however, performing more 

 than a mere repetition of it experimentally. 



From the great importance which, be it with justice or not, 

 is assigned by the majority of the philosophers of the present 

 day to -the decision of the question respecting the origin of 

 voltaic electricity, a more accurate examination of the process 

 in the Faradayan circuit appeared to me not to be without 

 value, and I therefore undertook the experiments, the results of 

 which will be enumerated in the following pages as briefly and 

 clearly as possible. 



Galvanic circuits of two fluids and two metals not in contact 

 may truly, as is readily conceived, be constructed without num- 

 ber. The English philosopher has examined a few, and these 

 few always composed only of zinc and platina with various 

 fluids. With this slight number of cases he always obtained 

 results favourable to his view. 



It appeared in the first instance to me to depend on this 

 point : let it be seen whether among the great number of possi- 

 ble cases there may not be some which could not be brought 

 under this ^deAv. If this question were affirmed by experiment, 

 another demand would arise ; namely, to subject Faraday's ex- 

 planation even for the apparently favourable cases to a more 

 rigorous examination. 



Above all, I considered a greater change with the metals to 

 be necessary, as, from long-known experience in other cases, it 

 seemed to me highly improbable that the negative metal of the 



* P. 81. It stands there, it is true, quite reversed, that tlie platina was 

 positive in the acid, and the zinc negative; but the connexion shows that this 

 is only founded in a permutation or typographical error. In this memoir that 

 metal is always termed positive which acts towards a second as zinc to coppeJ* 

 in the common circuit. 



