348 Mr Connex on the Action of 
with this particular view, and therefore am not entitled to make 
any other observations on Mr Farapay’s researches on them, 
than to observe that many of the experiments, particularly those 
with the chlorides and iodides of lead. (814, 818, 794), the chlo- 
ride of tin (819, 789), and the borate of lead (799), undoubtedly 
appear to lead to the establishment of this highly important 
principle with respect to other bodies than water. 
We must, however, take care that we do not extend our ideas 
of this definite action farther than any of the experiments which 
have been adduced in support of it by its author will warrant, a 
misconception into which I have reason to believe that some who 
have not fully considered. the evidence have fallen. One limit 
to it has been set, on the ground that the electric action itself is 
supposed to be capable of decomposing such bodies only as are 
composed of the same, or at least a like number of atoms of their 
elements, a point to which I shall presently advert. Accordingly 
there are no grounds whatever for holding that any definite 
action applies to such bodies as the great class of oxyacids and 
many other substances, admitted on all hands to consist of an 
unequal number of elementary atoms, and if such bodies are 
really undecomposable, no such definite action of course is pos- 
sible. But, farther, there is as yet no evidence of the applica- 
tion of definite voltaic action to the extensive class of ordinary 
salts consisting of an acid and an alkali, and yet many of them 
are composed of a like number of chemical equivalents, and are 
undeniably subject to electric decomposition. According to-the 
experiments hitherto made, the protoxides, water included, and 
the principal haloid salts, are the chief examples of the applica- 
tion of the law, and for this reason, that these are the principal 
substances on which the voltaic current operates. 
The point to which I have just alluded, whether the decom- 
posing agency of the electric fluid reaches only to substances 
composed of a like number of elementary atoms, is second only 
in importance to the law of definite action, and would require 
