founded on Experience. 101 



regards as depending upon chemical affinity, and which is 

 nianit'ested by the displacmg of the poles in the same man- 

 ner as with zinc : for instance, the acids go before the sul- 

 phurets aiid decide the oxygen pole (in the same way as with 

 lead, tin, he.) ; while with gold and platina the alkaline and 

 earthy sulpluirets assume the advantage even over the acids, 

 and leave to these 'last the hydrogen pole only. 



In treating of the Galvanic chain, M. Heidman has made 

 two distinct classes. 



He represents the former by tliis series : metal more ox- 

 idizahle — icatcr — melnl less oxidlzalle ; then the body com- 

 municating by immediate or intermediate contact with the 

 two solid conductors. In this chain the oxygen pole is al- 

 ways according to the direction in which the two solid hete- 

 rogeneous bodies touch the water. 



He represents the Galvanic chain of the second class hv 

 this other series : liquid which should oxidate — solid oxi- 

 dizable condiic/or — liquid simph/ a (ovdiiclor : then follow^ 

 the communication of the two heterogeneous liquids. 



Thus in a chain formed of silver — tcater — zinc — silver — 

 water — zinc, the first plate ((f silver and the last of zinc arc 

 (as he says) superfluous conductors; they cannot be consi- 

 dered as an essential part of the battery, since by these two 

 plates we only complete the chain; and the two chains of 

 six members are changed into a battery of two. Conse- 

 quently, when we form the pile with jjlales of copper and 

 zinc soldered, we should terminate it at the two extremities 

 by simple plates, in order to suppress superfluous conductors, 

 considering that it is not the placing of the copper or zinc 

 at one of these extremities which decides the hydrogen and 

 the oxygen pole, but only the respective disposition of the 

 two heterogeneous metals, and their contact with water. 

 Whence he concludes, that the plates by which we terminate 

 the pile are superfluous members of the battery, contrary 

 to- the opinion of Volta, Carlisle, Nicholson, Rcinhold, and 

 all those who admit that the Galvanic action is produced 

 only by the contact of two heterogeneous conductors, liijuid 

 or solid. 



We find in the third section a detail of the phsenomena 

 G 3 presented 



