the compound.

MRS. B.

That is true; but as the compound salt was known long before its basis
was discovered, it was very natural that when the earth was at length
separated from the acid, it should derive its name from the compound
from which it was obtained. However, to remove your scruples, we will
call the salt according to the new nomenclature, _sulphat of alumine_.
From this combination, alumine may be obtained in its pure state; it is
then soft to the touch, makes a paste with water, and hardens in the
fire. In nature, it is found chiefly in clay, which contains a
considerable proportion of this earth; it is very abundant in fuller's
earth, slate, and a variety of other mineral productions. There is
indeed scarcely any mineral substance more useful to mankind than
alumine. In the state of clay, it forms large strata of the earth, gives
consistency to the soil of valleys, and of all low and damp spots, such
as swamps and marshes. The beds of lakes, ponds, and springs, are almost
entirely of clay; instead of allowing of the filtration of water, as
sand does, it forms an impenetrable bottom, and by this means water is
accumulated in the caverns of the earth, producing those reservoirs
whence springs issue, and spout out at the surface.

EMILY.

I always thought that these subterraneous reservoirs of water were
bedded by some hard stone, or rock, which the water could not penetrate.

MRS. B.

That is not the case; for in the course of time water would penetrate,
or wear away silex, or any other kind of stone, while it is effectually
stopped by clay, or alumine.

The solid compact soils, such as are fit for corn, owe their consistence
in a great measure to alumine; this earth is therefore used to improve
sandy or chalky soils, which do not retain a sufficient quantity of
water for the purpose of vegetation.

Alumine is the most essential ingredient in all potteries. It enters
into the composition of brick, as well as that of the finest porcelain;
the addition of silex and water hardens it, renders it susceptible of a
degree of vitrification, and makes it perfectly fit for its various
purposes.

CAROLINE.

I can scarcely conceive that brick and china should be made of the same
materials.

MRS. B.

Brick consists almost entirely of baked clay; but a certain proportion
of silex is essential to the formation of earthen or stone ware. In
common potteries sand is used for that purpose; a more pure silex i