top-cocks, by one of which a
stream of water is thrown into the vessel through a long funnel, whilst
by the other the gas is forced out through a blow-pipe adapted to it, as
the water gains admittance. --Now that I pour water into the funnel, you
may hear the gas issuing from the blow-pipe--I bring the charcoal close
to the current, and drop the filings upon it--

CAROLINE.

They emit much the same vivid light as the combustion of the iron wire
in oxygen gas.

MRS. B.

The process is, in fact, the same; there is only some difference in the
mode of conducting it. Let us burn some tin in the same manner--you see
that it is equally combustible. --Let us now try some copper--

CAROLINE.

This burns with a greenish flame; it is, I suppose, owing to the colour
of the oxyd?

EMILY.

Pray, shall we not also burn some gold?

MRS. B.

That is not in our power, at least in this way. Gold, silver, and
platina, are incapable of being oxydated by the greatest heat that we
can produce by the common method. It is from this circumstance, that
they have been called perfect metals. Even these, however, have an
affinity for oxygen; but their oxydation or combustion can be performed
only by means of acids or by electricity. The spark given out by the
Voltaic battery produces at the point of contact a greater degree of
heat than any other process; and it is at this very high temperature
only that the affinity of these metals for oxygen will enable them to
act on each other.

I am sorry that I cannot show you the combustion of the perfect metals
by this process, but it requires a considerable Voltaic battery. You
will see these experiments performed in the most perfect manner, when
you attend the chemical lectures of the Royal Institution. But in the
mean time I can, without difficulty, show you an ingenious apparatus
lately contrived for the purpose of producing intense heats, the power
of which nearly equals that of the largest Voltaic batteries. It simply
consists, you see, in a strong box, made of iron or copper, (PLATE X.
fig. 2.) to which may be adapted this air-syringe or condensing-pump,
and a stop-cock terminating in a small orifice similar to that of a
blow-pipe. By working the condensing syringe, up and down in this
manner, a quantity of air is accumulated in the vessel, which may be
increased to almost any extent; so that if we now turn the stop-cock,
the condensed air will rush out, forming a jet of considerable f