roduced in its greatest degree of purity it can only exist under the
gasseous form, at least in the usual temperature of the atmosphere, it
has an excessively penetrating smell, is absorbed in large quantities by
water, especially if cold and assisted by compression. Water thus
saturated with ammoniac has usually been termed volatile alkaline fluor;
we shall call it either simply ammoniac, or liquid ammoniac, and
ammoniacal gas when it exists in the aeriform state.

Sec. 4. _Of Lime, Magnesia, Barytes, and Argill._

The composition of these four earths is totally unknown, and, until by
new discoveries their constituent elements are ascertained, we are
certainly authorised to consider them as simple bodies. Art has no share
in the production of these earths, as they are all procured ready
formed from nature; but, as they have all, especially the three first,
great tendency to combination, they are never found pure. Lime is
usually saturated with carbonic acid in the state of chalk, calcarious
spars, most of the marbles, &c.; sometimes with sulphuric acid, as in
gypsum and plaster stones; at other times with fluoric acid forming
vitreous or fluor spars; and, lastly, it is found in the waters of the
sea, and of saline springs, combined with muriatic acid. Of all the
salifiable bases it is the most universally spread through nature.

Magnesia is found in mineral waters, for the most part combined with
sulphuric acid; it is likewise abundant in sea-water, united with
muriatic acid; and it exists in a great number of stones of different
kinds.

Barytes is much less common than the three preceding earths; it is found
in the mineral kingdom, combined with sulphuric acid, forming heavy
spars, and sometimes, though rarely, united to carbonic acid.

Argill, or the base of alum, having less tendency to combination than
the other earths, is often found in the state of argill, uncombined with
any acid. It is chiefly procurable from clays, of which, properly
speaking, it is the base, or chief ingredient.

Sec. 5. _Of Metallic Bodies._

The metals, except gold, and sometimes silver, are rarely found in the
mineral kingdom in their metallic state, being usually less or more
saturated with oxygen, or combined with sulphur, arsenic, sulphuric
acid, muriatic acid, carbonic acid, or phosphoric acid. Metallurgy, or
the docimastic art, teaches the means of separating them from these
foreign matters; and for this purpose we refer to