On Chemical Philosophy. 57 
plied to compound substances.” The different elements of these 
compounds are gradually dissolved in the order of their solu- 
bility ; and when we come to chemical affinity, we shall show how 
this explains the decompositions and combinations of substances. 
It is evident that Fourcroy considered the gases as the solution 
of substances in ealoric ; for he never speaks of the separation of 
the particles to a greater distance, as that which constituted the 
gaseous or liquid forms. Indeed Dr, Thomson has wisely given 
up this in the last edition of his System. It would therefore be 
the less necessary to insist on this, were it not that I conceive it 
is preparing the way for the explanation of some cases where no 
theory has yet been offered at all worthy of the name. I allude 
to galvanism in particular. How separating the particles of 
matter, by the power of repulsion, ean ever produce the gaseous 
or liquid forms, is one of those things ] coyld never understand, 
nor have | yet met with one who could. Men may profess ta 
believe what is the faith of the schools ; but unless the under- 
standing be convinced, it is mere profession. The mere mecha- 
nical separation of the particles ean obviously never change the 
quality of substances; but solution and combination with a 
power which produces every effect must change their properties. 
The argument in favour of the doctrine of repulsion, whick 
says, that but for such a power all bodies must be equally solid, 
is mere assertion without meaning—all bodies are not the same. 
It is said that the particles of matter do not touch each other, 
because some few can be pressed into smaller space; and that 
therefore they are held together in this state by some repulsive 
power: But neither of these inferences at all follows. Caloric 
fills up the insterstices, and caloric is something material; it may 
be beat or squeezed out, as all metals in this way evolve heat. 
It is very probable that the particles of matter themselves may 
not touch at all points ;—-but why talk about such points, when 
we neither know what they are, nor what they are like, as is too 
swell proved by the various controversies respecting them? We 
shall, notwithstanding this, recur to the subject when we come to 
chemical affinjty. Let us be careful, however, lest we waste our 
time and talents on mere speculative points, There is enough 
to do in philosophy without this. 
** Heat,” says Chaptal, “ by combining with bodies, pro- 
duces an effect the very opposite of attraction; and we might 
consider ourselves as authorized to affirm that it is a principle 
of repulsion, if sound chemistry had not proved that it produces 
these effects only by its endeavour to combine with bodies, and 
thereby necessarily diminishing the force of aggregation, as all other 
chemical agents do. Besides which, the extreme levity of caloric 
produces 
