250 Definition of Chemistry. 
tion in the action of substances on each other, he will infer 
that the action is not chemical, whereas the greater number 
of cases of combination, are attended with more or less of 
sensible motion. ‘Thus, when we pour nitric acid on chalk, 
a violent effervescence ensues. Is the phenomenon therefore 
not chemical? The motion is, indeed, mechanical. It arises 
om an elastic substance, (carbonic acid,) making its way 
through the fluid ; while alJ that is strictly chemical, namely, 
the union of the particles of the acid with those of the lime, is, 
it is true, imperceptible. Still it is accompanied by a sensible 
motion; and the student must have made considerable pro- 
ficiency in the science, before he will be able to make the 
necessary distinction. The definition, which appears to me 
to convey to the learner the clearest views of the peculiar 
province of the chemist, is that which represents him as oc- 
cupied with the changes which take place among the parti- 
cles of matter, in distinction from masses,—as employed in 
resolving compound substances into their elements, and ani- 
ting simples into compounds, hen a new substance is 
presented to him, his first inquiry is, is it simple or compound ? 
and his second is, what changes is it capable of effecting in 
Other chemical agents, or of sustaining from them? as wheth- 
er it is fusible by heat, or soluble in an acid. If he can re- 
solve it into two substances, he proceeds next to ascertain the 
peculiar properties and relations of each of these, by investi~ 
gating, as was done with the compound, the changes it is ca- 
pable of eflecting in other chemical agents, or of sustaining 
from them. Hence, the following definition appears to me 
to express as much of these peculiarities of the science, as is 
capable of being comprehended in so short a space. <3 
Chemistry investigates the composition of bodies, and the 
changes of constitution, which they produce by their action on 
each othe my fault can be found with this defini 
‘Hon, it is, that it does not bring distinctly into view those 
: i 
‘al power 
and electricity, by the agenc 
which all chemical phenomen 
in which these ultimate powers act, constitute the first princi- 
ples of the science, or its laws; and the greater part of the 
reasonings of the chemist, consists in tracing individual phe- 
a to the operation of one or the other of these laws. 
ts for the melting of snow, by ascribing it to 
is one of the known properties or laws of 
* See Ure’s Dictionary. 
