Atomic Theory. 7 
other. The laws of definite proportions are a class of facts 
established by rigorous experiments : the object of the Ato- 
mic Theory is to account for those facts. It is a very in- 
genious structure, and derives a high probability from its af- 
fording so complete an explanation of the foregoing laws of 
attraction ; but were the whole doctrine of atoms discarded, 
the truth of the pee rae respecting definite proportions | 
would remain unsha 
The Atomic Blaby proceeds on the supposition that every 
body is an assemblage of minute solid particles, which, al- 
though they may be divisible, at least mathematically, are 
still’no longer divided ; and that when different elements 
unite, forming — compounds, these particles, and not 
masses, combine with one another. It is not, therefore, 
opposed to the midithetheabad doctrine of the infinite divisi- 
bility of matter ; it only assumes that matter is not, in fact, 
- infinitely divided. These undivided particles are the atoms 
in question. In how many respects these ultimate parts of 
different bodies — differ from each other, we do not know ; 
but, for explaining the phenomena of definite _ proportions, 
it is only necessary to assume that they differ from each oth- 
er in weight. “Grant then that aapaneed bodies are formed 
by a union of atoms of the foregoing description, and let us 
see how this fact may be applied to account for the phenom- 
ena of definite _proportions. — To recur to an exam le al 
sad diverse from each other. They are, Nitrous Aiwies 
Nitric Oxide, Nitrous Acid Gas, Nitrous Acid, and 
Acid. If we take a given quantity of Nitrogen, Reece sen 
grains, and combine it with five grains of Oxygen, we fo 
Nitrous Oxide ; with five more, and we have Nitric Oxide ; 
with five more, Nitrous Acid Gas ; with five more, Niteous 
Acid ; and with five more, Nitric Acid. Nor is it known 
that any other combinations of these two elements exist. 
Now suppose that these several com are formed by 
the union of-a certain number of atoms of nitrogen with a 
certain number of atoms oe oxygen, the latter number va 
the several compounds, how is it probable that the 
atoms unite to form the first compound ? The most sinew 
combination possible would be the union of an e 
ber of atoms of each element. It is plain that one atom ee 
nitrogen can combine with no less than one atom of oxygen, 
