OHM ON THE GALVANIC CIRCUIT. 503 



mically changeable portion, which are in connexion with the 

 other chemically unchangeable parts of the circuit, undergoing 

 a gradual change during the decomposition till they arrive at 

 their permanent state, giving rise at those places to an altered 

 tension. If, for instance, we call ? the value of r, which 

 belongs to all places of the extent in question, before chemical 

 change has begun in it, and designate the cocfHcient of the ten- 

 sion occurring at the extremities of this extent, supposing that 

 it is the same at both ends, by ■$", and moreover express by /* 

 and V the latent electroscopic forces of those places of the che- 

 mically unalterable part of the circuit which are situated adja- 

 cent to the chemically changeable extent, the tensions existing at 

 these places can be determined individually. They are, namely, 

 previous to the commencement of chemical change, the fol- 

 lowing : 



^" [l"- ~ (^ + (*** — '*) ?)]? ^"d 



<p" l{)i+{m-n) ?)-v] ; 

 and after the permanent state in the decomposition has been 

 attained, if we, as above, let s' and z'' be those values of z 

 which belong in this state to those places, they are the fol- 

 lowing : 



4"" [i^ — {n+ (m — n) z')], and 



<$>" [{n +{m — n) z") - v], 



their sum is therefoi'e in one case 



<p"{l^-v), 

 and in the other 



^" (f^ - v) + 45" {m - n) {z" - z') ; 

 consequently the increase of tension at those places is 



<p"{m-n) {z"-z'). 

 If we add this change of the tension to that above found, we 

 obtain for the entire difference of the tension, produced by the de- 

 composition until the commencement of the permanent state, 



(<f)" — <f)') (m — n) {z" —z'), 

 which, if we substitute <J> for <$>" — <$', changes into 



4> {n—m) (z" —z). 

 If now we represent by S the magnitude of the curi-ent, and by 

 A the sum of the tensions in the circuit, before any chemical 

 change has commenced, by S' the magnitude of the current, 

 after the permanent state has been attained ; lastly, by L the 



2 L 2 



