n known but for a short time, and the names of which
had not yet received the sanction of the public; and, secondly, when the
names which had been adopted, whether by the ancients or the moderns,
appeared to us to express evidently false ideas, when they confounded
the substances, to which they were applied, with others possessed of
different, or perhaps opposite qualities. We made no scruple, in this
case, of substituting other names in their room, and the greatest number
of these were borrowed from the Greek language. We endeavoured to frame
them in such a manner as to express the most general and the most
characteristic quality of the substances; and this was attended with the
additional advantage both of assisting the memory of beginners, who find
it difficult to remember a new word which has no meaning, and of
accustoming them early to admit no word without connecting with it some
determinate idea.

To those bodies which are formed by the union of several simple
substances we gave new names, compounded in such a manner as the nature
of the substances directed; but, as the number of double combinations is
already very considerable, the only method by which we could avoid
confusion, was to divide them into classes. In the natural order of
ideas, the name of the class or genus is that which expresses a quality
common to a great number of individuals: The name of the species, on the
contrary, expresses a quality peculiar to certain individuals only.

These distinctions are not, as some may imagine, merely metaphysical,
but are established by Nature. "A child," says the Abbe de Condillac,
"is taught to give the name _tree_ to the first one which is pointed out
to him. The next one he sees presents the same idea, and he gives it the
same name. This he does likewise to a third and a fourth, till at last
the word _tree_, which he first applied to an individual, comes to be
employed by him as the name of a class or a genus, an abstract idea,
which comprehends all trees in general. But, when he learns that all
trees serve not the same purpose, that they do not all produce the same
kind of fruit, he will soon learn to distinguish them by specific and
particular names." This is the logic of all the sciences, and is
naturally applied to chemistry.

The acids, for example, are compounded of two substances, of the order
of those which we consider as simple; the one constitutes acidity, and
is common to all acids, and, from this