I will make it still hotter, and now we get more of it, so that I can
actually pour the vapour out of the flask into that basin, and set it on
fire there. This, then, is exactly the same kind of vapour as we have in
the middle of the candle; and that you may be sure this is the case, let
us try whether we have not got here, in this flask, a real combustible
vapour out of the middle of the candle. [Taking the flask into which the
tube from the candle proceeded, and introducing a lighted taper.] See how
it burns. Now, this is the vapour from the middle of the candle, produced
by its own heat; and that is one of the first things you have to consider
with respect to the progress of the wax in the course of its combustion,
and as regards the changes it undergoes. I will arrange another tube
carefully in the flame, and I should not wonder if we were able, by a
little care, to get that vapour to pass through the tube to the other
extremity, where we will light it, and obtain absolutely the flame of the
candle at a place distant from it. Now, look at that. Is not that a very
pretty experiment? Talk about laying on gas why, we can actually lay on a
candle! And you see from this that there are clearly two different kinds
of action one the _production_ of the vapour, and the other the
_combustion_ of it both of which take place in particular parts of the
candle.
[Illustration: Fig. 8]
I shall get no vapour from that part which is already burnt. If I raise
the tube (fig. 7) to the upper part of the flame, so soon as the vapour
has been swept out, what comes away will be no longer combustible: It is
already burned. How burned? Why, burned thus: In the middle of the flame,
where the wick is, there is this combustible vapour; on the outside of the
flame is the air which we shall find necessary for the burning of the
candle; between the two, intense chemical action takes place, whereby the
air and the fuel act upon each other, and at the very same time that we
obtain light the vapour inside is destroyed. If you examine where the heat
of a candle is, you will find it very curiously arranged. Suppose I take
this candle, and hold a piece of paper close upon the flame, where is the
heat of that flame? Do you not see that it is _not_ in the inside? It is
in a ring, exactly in the place where I told you the chemical action was;
and even in my irregular mode of making the experiment, if there is not
too much disturbance, there will always be a ring. This is a good
experiment for you to make at home. Take a strip of paper, have the air in
the room quiet, and put the piece of paper right across the middle of the
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