ot, by the burning
of the gas within the lamp?

MRS. B.

And this is actually the case, for the top of the lamp is very apt to
become red-hot. But, fortunately, inflammable gaseous mixtures cannot be
exploded by red-hot wire, the intervention of actual flame being
required for that purpose; so that the wire does not set fire to the
explosive gas around it.

EMILY.

I can understand that; but if the wire be red-hot, how can it cool the
flame within, and prevent its passing through the gauze?

MRS. B.

The gauze, though red-hot, is not so hot as the flame by which it has
been heated; and as metallic wire is a good conductor, the heat does not
much accumulate in it, as it passes off quickly to the other parts of
the lamp, as well as to any contiguous bodies.

CAROLINE.

This is indeed a most interesting discovery, and one which shows at once
the immense utility with which science may be practically applied to
some of the most important purposes.

CONVERSATION VIII.

ON SULPHUR AND PHOSPHORUS.

MRS. B.

SULPHUR is the next substance that comes under our consideration. It
differs in one essential point from the preceding, as it exists in a
solid form at the temperature of the atmosphere.

CAROLINE.

I am glad that we have at last a solid body to examine; one that we can
see and touch. Pray, is it not with sulphur that the points of matches
are covered, to make them easily kindle?

MRS. B.

Yes, it is; and you therefore already know that sulphur is a very
combustible substance. It is seldom discovered in nature in a pure
unmixed state; so great is its affinity for other substances, that it is
almost constantly found combined with some of them. It is most commonly
united with metals, under various forms, and is separated from them by a
very simple process. It exists likewise in many mineral waters, and some
vegetables yield it in various proportions, especially those of the
cruciform tribe. It is also found in animal matter; in short, it may be
discovered in greater or less quantity, in the mineral, vegetable, and
animal kingdoms.

EMILY.

I have heard of _flowers of sulphur_, are they the produce of any plant?

MRS. B.

By no means: they consist of nothing more than common sulphur, reduced
to a very fine powder by a process called _sublimation_. --You see some
of it in this phial; it is exactly the same substance as this lump of
sulphur, only its colour is a paler yellow, owing to its sta