Cases of Voltaic Action. 431 
sity, which is only equal to that necessary to cause the current 
to pass through it, we are unable to observe it. 
From these and other observations of a similar kind, I be- 
lieve it may be stated as a general law, that when a current 
passes through a series of conductors, it induces a state of 
things, capable of producing a current equal to itself in 
amount, and opposite in direction; provided the changes pro- 
duced are permanent. 
This law can be proved to hold in all cases where a liquid 
forms part of the circuit, with the single exception of the case 
where two pieces of the same metal communicate by means of 
one of its salts; here the phenomena are the same as if the 
metallic circuit were complete. (Faraday.) 
These results appear to show that there is something of the 
nature of a force transmitted through the circuit, and the 
phzenomena of tension lend great support to this idea, for here 
we have bodies actually put in motion. 
If now we suppose each chemical molecule to be capable of 
exerting an attractive force on every other molecule in its vi- 
cinity, the phznomena of the voltaic circuit are precisely 
what should result from such an attraction, and voltaic ac- 
tion appears to be chemical action under another form; the 
action in one case taking place between molecules in contact, 
or at extremely small distances, and in the other between those 
at a considerable and sensible distance. 
Ifany number of molecules of different substances be placed 
near each other, and in such a state as to admit of their free 
motion, they arrange themselves so that their attractive forces 
produce a state of equilibrium, and till this state is attained 
the molecules are in a constrained condition. Thus when 
chlorine, hydrogen and water are brought into contact, the 
hydrogen and chlorine unite to form hydrochloric acid, and 
this is the state of equilibrium. The mode in which this state 
Water 
GiXo)} = 
atom of Cl unites with the H previously in combination with 
the O as water, while the O unites with the free H, and Cl H 
and H O are formed; if, however, the H and Cl are at some 
distance from each other, as when separated by water, the 
(Fig. 2.) @O@OWC), action cannot take place, for the 
molecules cannot assume such an arrangement as would form 
a complete circuit, without which they cannot exert their at- 
tractions, but if Hand Cl be united by a metal (Fig. 3.) 
is attained seems to be as follows:—(Fig. 1.) cx } 23 the 
