balance, and which we can take account of as to hundredweights and as to
tons, as you will see almost immediately.

Now, as regards this very property of oxygen supporting combustion, which
we may compare to air, I will take a piece of candle to shew it you in a
rough way, and the result will be rough. There is our candle burning in
the air: how will it burn in oxygen? I have here a jar of this gas, and I
am about to put it over the candle for you to compare the action of this
gas with that of the air. Why, look at it: it looks something like the
light you saw at the poles of the voltaic battery. Think how vigorous that
action must be! And yet, during all that action, nothing more is produced
than what is produced by the burning of the candle in air. We have the
same production of water, and the same phenomena exactly, when we use this
gas instead of air, as we have when the candle is burnt in air.

But now we have got a knowledge of this new substance, we can look at it a
little more distinctly, in order to satisfy ourselves that we have got a
good general understanding of this part of the product of a candle. It is
wonderful how great the supporting powers of this substance are as regards
combustion. For instance, here is a lamp which, simple though it be, is
the original, I may say, of a great variety of lamps which are constructed
for divers purposes--for light-houses, microscopic illuminations, and
other uses; and if it were proposed to make it burn very brightly, you
would say, "If a candle burnt better in oxygen, will not a lamp do the
same?" Why, it will do so. Mr. Anderson will give me a tube coming from
our oxygen reservoir, and I am about to apply it to this flame, which I
will previously make burn badly on purpose. There comes the oxygen: what a
combustion that makes! But if I shut it off, what becomes of the lamp? [The
flow of oxygen was stopped, and the lamp relapsed to its former dimness.]
It is wonderful how, by means of oxygen, we get combustion accelerated.
But it does not affect merely the combustion of hydrogen, or carbon, or
the candle; but it exalts all combustions of the common kind. We will take
one which relates to iron, for instance, as you have already seen iron
burn a little in the atmosphere. Here is a jar of oxygen, and this is a
piece of iron wire; but if it were a bar as thick as my wrist, it would
burn the same.

[Illustration: Fig. 23.]

I first attach a little piece of wood to the