marked in the oxygen we obtained by means of the voltaic battery from
water, we may expect to find the same property here. We will try it You
see there is the combustion of a lighted taper in air, and here is its
combustion in this gas [lowering the taper into the jar]. See how brightly
and how beautifully it burns! You can also see more than this, you will
perceive it is a heavy gas, whilst the hydrogen would go up like a
balloon, or even faster than a balloon, when not encumbered with the
weight of the envelope.
[Illustration: Fig. 22.]
You may easily see that although we obtained from water twice as much in
volume of the hydrogen as of oxygen, it does not follow that we have twice
as much in weight because one is heavy, and the other a very light gas.
We have means of weighing gases or air; but without stopping to explain,
that, let me just tell you what their respective weights are. The weight
of a pint of hydrogen is three-quarters of a grain; the weight of the same
quantity of oxygen is nearly twelve grains. This is a very great
difference. The weight of a cubit foot of hydrogen is one-twelfth of an
ounce; and the weight of a cubit foot of oxygen is one ounce and a third.
And so on we might come to masses of matter which may be weighed in the
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
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