explosion, or a _detonation_ (as chemists commonly call it), will be
produced. For this purpose, I need only take up the receiver, and
quickly present its open mouth to the candle---- so . . . .

CAROLINE.

It produced only a sort of hissing noise, with a vivid flash of light.
I had expected a much greater report.

MRS. B.

And so it would have been, had the gases been closely confined at the
moment they were made to explode. If, for instance, we were to put in
this bottle a mixture of hydrogen gas and atmospheric air; and if, after
corking the bottle, we should kindle the mixture by a very small
orifice, from the sudden dilatation of the gases at the moment of their
combination, the bottle must either fly to pieces, or the cork be blown
out with considerable violence.

CAROLINE.

But in the experiment which we have just seen, if you did not kindle the
hydrogen gas, would it not equally combine with the oxygen?

MRS. B.

Certainly not; for, as I have just explained to you, it is necessary
that the oxygen and hydrogen gases be burnt together, in order to
combine chemically and produce water.

CAROLINE.

That is true; but I thought this was a different combination, for I see
no water produced.

MRS. B.

The water resulting from this detonation was so small in quantity, and
in such a state of minute division, as to be invisible. But water
certainly was produced; for oxygen is incapable of combining with
hydrogen in any other proportions than those that form water; therefore
water must always be the result of their combination.

If, instead of bringing the hydrogen gas into sudden contact with the
atmosphere (as we did just now) so as to make the whole of it explode
the moment it is kindled, we allow but a very small surface of gas to
burn in contact with the atmosphere, the combustion goes on quietly and
gradually at the point of contact, without any detonation, because the
surfaces brought together are too small for the immediate union of
gases. The experiment is a very easy one. This phial, with a narrow
neck, (PLATE VIII. fig. 5.) is full of hydrogen gas, and is carefully
corked. If I take out the cork without moving the phial, and quickly
approach the candle to the orifice, you will see how different the
result will be----

EMILY.

How prettily it burns, with a blue flame! The flame is gradually sinking
within the phial--now it has entirely disappeared. But does not this
combustion likewise produ