production of flame. They will each burn separately. [The Lecturer then
ignited the mixture.] There is the gunpowder, which burns with a flame;
and there are the filings--they burn with a different kind of combustion.
You see, then, these two great distinctions; and upon these differences
depend all the utility and all the beauty of flame which we use for the
purpose of giving out light. When we use oil, or gas, or candle, for the
purpose of illumination, their fitness all depends upon these different
kinds of combustion.

There are such curious conditions of flame, that it requires some
cleverness and nicety of discrimination to distinguish the kinds of
combustion one from another. For instance, here is a powder which is very
combustible, consisting, as you see, of separate little particles. It is
called _lycopodium_[7], and each of these particles can produce a vapour,
and produce its own flame; but, to see them burning, you would imagine it
was all one flame. I will now set fire to a quantity, and you will see the
effect. We saw a cloud of flame, apparently in one body; but that rushing
noise [referring to the sound produced by the burning] was a proof that
the combustion was not a continuous or regular one. This is the lightning
of the pantomimes, and a very good imitation. [The experiment was twice
repeated by blowing lycopodium from a glass tube through a spirit-flame.]
This is not an example of combustion like that of the filings I have been
speaking of, to which we must now return.

Suppose I take a candle, and examine that part of it which appears
brightest to our eyes. Why, there I get these black particles, which
already you have seen many times evolved from the flame, and which I am
now about to evolve in a different way. I will take this candle and clear
away the gutterage, which occurs by reason of the currents of air; and if
I now arrange a glass tube so as just to dip into this luminous part, as