other jar; but you see this is not so distinctly red as the first: and,
further, this curious thing happens,--if I take these two gases and shake
them well together with water, we shall absorb the red gas; and then, if I
put in more of this test-gas and shake again, we shall absorb more; and I
can go on as long as there be any oxygen present to produce that effect.
If I let in air, it will not matter; but the moment I introduce water, the
red gas disappears; and I may go on in this way, putting in more and more
of the test-gas, until I come to something left behind which will not
redden any longer by the use of that particular body that rendered the air
and the oxygen red. Why is that? You see in a moment it is because there
is, besides oxygen, something else present which is left behind. I will
let a little more air into the jar, and if it turns red you will know that
some of that reddening gas is still present, and that consequently it was
not for the want of this producing body that that air was left behind.

Now, you will begin to understand what I am about to say. You saw that
when I burnt phosphorus in a jar, as the smoke produced by the phosphorus
and the oxygen of the air condensed, it left a good deal of gas unburnt,
just as this red gas left something untouched,--there was, in fact, this
gas left behind, which the phosphorus cannot touch, which the reddening
gas cannot touch, and this something is not oxygen, and yet is part of the
atmosphere.

So that is one way of opening out air into the two things of which it is
composed--oxygen, which burns our candles, our phosphorus, or anything
else; and this other substance--nitrogen--which will not burn them. This
other part of the air is by far the larger proportion, and it is a very
curious body, when we come to examine it; it is remarkably curious, and
yet you say, perhaps, that it is very uninteresting. It is uninteresting
in some respects because of this--that it shews no brilliant effects of