ertain quantity of water,
which is supposed essential to its formation. So that, in the experiment
just mentioned, this water is supplied by the union of the hydrogen gas
with the oxygen of the oxy-muriatic acid; and therefore the mixture
resolves itself into the base of muriatic acid and water, that is,
muriatic acid gas.

CAROLINE.

I think the old theory must be the true one; for otherwise how could you
explain the formation of oxy-muriatic gas, from a mixture of muriatic
acid and oxyd of manganese?

MRS. B.

Very easily; you need only suppose that in this process the muriatic
acid is decomposed; its hydrogen unites with the oxygen of the manganese
to form water, and the chlorine appears in its separate state.

EMILY.

But how can you explain the various combustions which take place in
oxy-muriatic gas, if you consider it as containing no oxygen?

MRS. B.

We need only suppose that combustion is the result of intense chemical
action; so that chlorine, like oxygen, in combining with bodies, forms
compounds which have less capacity for caloric than their constituent
principles, and, therefore, caloric is evolved at the moment of their
combination.

EMILY.

If, then, we may explain every thing by either theory, to which of the
two shall we give the preference?

MRS. B.

It will, perhaps, be better to wait for more positive proofs, if such
can be obtained, before we decide positively upon the subject. The new
doctrine has certainly gained ground very rapidly, and may be considered
as nearly established; but several competent judges still refuse their
assent to it, and until that theory is very generally adopted, it may be
as well for us still occasionally to use the language to which chemists
have long been accustomed. --But let us proceed to the examination of
salts formed by muriatic acid.

Among the compound salts formed by muriatic acid, the _muriat of soda_,
or common salt, is the most interesting.* The uses and properties of
this salt are too well known to require much comment. Besides the
pleasant flavour it imparts to the food, it is very wholesome, when not
used to excess, as it assists the process of digestion.

Sea-water is the great source from which muriat of soda is extracted by
evaporation. But it is also found in large solid masses in the bowels of
the earth, in England, and in many other parts of the world.

[Footnote *: According to Sir H. Davy's views of the nature of the