Mr. Davy’s Hypothesis of Electro-chemical Affinity. 253 
electricity which is supposed to cause combination has been 
already shown. Whether it be a conductor of such in- 
tensities as the Voltaic, is perfectly immaterial to the in- 
quirv. When in the saline solution are immersed the 
polar wires, the Jatter as usual exert their attractions in 
concert to the opposite electricities of the saline elements, 
Tt becomes a question, Why do not the electricities of the 
decomposed elements pass through the fluid conducting 
medium towards the poles, without carrying also the cle- 
ments with which they were combined? tor the original 
electricity of the elements is immediately annihilated in its 
passage towards the poles. Consequently all attraction 
between it and the element with which it was combined, 
must be destroyed. Besides, in all our experiments, we 
find that to produce attraction or repnision it is necessary 
to have an electric interposed between the body acting and 
the body acted on. 
It is next to be examined how far decomposition can be 
effected in the manner stated. 
It is an axiom, that a force cannot be overcome. by a 
force which is not greater. Then, if a quantity of artificial 
electricity thrown into a compound occasion decomposition, 
that electricity must be possessed of superior intensity. We 
will suppose it the positive power thrown mto solution of 
sulphate of potash. The first effort of the superadded 
power will be to attract the negative acid, which will be- 
come ‘saturated or neutral. The second effort will be to 
combine with, and to exist sensibly and absolutely in, the 
neutral acid. Thus the acid which was, in the combination, 
negative, is now positive. The alkalisuffers this change con- 
versely, and becomes negative. We have now all the con- 
ditions as they primarily existed for producing combination ; 
with this difference only, that the attractions of the bodies 
are by far more intense; for, if otherwise, the original com- 
bination would never have been broken. Why then do 
they not combine with increased force? And why are 
they attracted to these very poles, which being im similar 
states should violently repel them? Independently of in- 
creased intensity there are two powerful causes operating to 
favour combination; one only of which tended to sustain 
the original salt. First, the bodies are forced to approach 
directly by their reciprocal attractions; and indirectly by 
the strong repulsion of the similarly electrified poles. Cou- 
sequently they should pass. to, and occupy the situation in, 
the fluid where there is least resistance; namely, the mid 
dle point, where the repulsion of one pole enus ai. tic 
: ; attraction 
= 
ai 
