er gas, when I apply a lighted
taper to the mouth of the flask I get a large flame (Fig. 29). There it
is! The more gas I evolve (that is, the more actively I apply the heat)
the larger is the flame. You see it is a very large flame now. If I take
the spirit lamp away, the production of gas grows less and less, until
my flame almost dies out; but you see if I again apply my heat and set
more gas free, I revive my flame. I want you to grasp this very
important fact, upon which I cannot enlarge further now, that given
flame, I must have a gas to burn, and therefore heat as a power is
needed before I can obtain flame.

[Illustration: Fig. 29.]

Well, you ask me, is that true of all flame? Where is the gas, you say,
in that candle flame? Think for a moment of the science involved in
lighting a candle. What am I doing when I apply a lighted match to this
candle? The first thing I do is to melt the tallow, the melted tallow
being drawn up by the capillarity of the wick. The next thing I do is to
convert the liquid tallow into a gas. This done, I set fire to the gas.
I don't suppose you ever thought so much was involved in lighting a
candle. My candle is nothing more than a portable gas-works, similar in
principle to the gas-works from which the gas that I am burning here is
supplied. Whether it is a lamp, or a gas-burner, or a candle, they are
all in a true sense gas-works, and they all pre-suppose the application
of heat to some material or another for the purpose of forming a gas
which will burn.

[Illustration: Fig. 30.]

Before I pass on, I want to refer to the beautiful burner that I have
here. It is the burner used by the Whitechapel stall-keepers on a
Saturday night (Fig. 30). (Fig. _a_ is an enlarged drawing of the
burner.) Just let me explain the science of the Whitechapel burner.
First of all you will see the man with a funnel filling this top portion
with naphtha (_c_). Here is a stop-cock, by turning which he lets a
little naphtha run down the tube through a very minute orifice into this
small cup at the bottom of the burner (_a_). This cup he heats in a
friend's lamp, thereby converting the liquid naphtha, which runs into
the cup, into a gas. So soon as the gas is formed--in other words, so
soon as the naphtha has been sufficiently heated--the naphtha gas
catches fire, the heat being then sufficient to maintain that little cup
hot enough to keep up a regular supply of naphtha gas. When the lamp
does not