arrogate, derive their chief
chemical properties. In this combination, the sulphur, together with the
iron, have so strong an attraction for oxygen, that they obtain it both
from the air and from water, and by condensing it in a solid form,
produce the heat which raises the temperature of the water in such a
remarkable degree.

EMILY.

But if pyrites obtain oxygen from water, that water must suffer a
decomposition, and hydrogen gas be evolved.

MRS. B.

That is actually the case in the hot springs alluded to, which give out
an extremely fetid gas, composed of hydrogen impregnated with sulphur.

CAROLINE.

If I recollect right, steel and plumbago, which you mentioned in the
last lesson, are both carburets of iron?

MRS. B.

Yes; and they are the only carburets of much consequence.

A curious combination of metals has lately very much attracted the
attention of the scientific world: I mean the meteoric stones that fall
from the atmosphere. They consist principally of native or pure iron,
which is never found in that state in the bowels of the earth; and
contain also a small quantity of nickel and chrome, a combination
likewise new in the mineral kingdom.

These circumstances have led many scientific persons to believe that
those substances have fallen from the moon, or some other planet, while
others are of opinion either that they are formed in the atmosphere, or
are projected into it by some unknown volcano on the surface of our
globe.

CAROLINE.

I have heard much of these stones, but I believe many people are of
opinion that they are formed on the surface of the earth, and laugh at
their pretended celestial origin.

MRS. B.

The fact of their falling is so well ascertained, that I think no person
who has at all investigated the subject, can now entertain any doubt of
it. Specimens of these stones have been discovered in all parts of the
world, and to each of them some tradition or story of its fall has been
found connected. And as the analysis of all those specimens affords
precisely the same results, there is strong reason to conjecture that
they all proceed from the same source. It is to Mr. Howard that
philosophers are indebted for having first analysed these stones, and
directed their attention to this interesting subject.

CAROLINE.

But pray, Mrs. B., how can solid masses of iron and nickel be formed
from the atmosphere, which consists of the two airs, nitrogen and
oxygen?

MRS. B.

I