lloons are filled with this gas, and if they carried no other
weight than their covering, would ascend as rapidly as these bubbles.

CAROLINE.

Yet their covering must be much heavier than that of these bubbles?

MRS. B.

Not in proportion to the quantity of gas they contain. I do not know
whether you have ever been present at the filling of a large balloon.
The apparatus for that purpose is very simple. It consists of a number
of vessels, either jars or barrels, in which the materials for the
formation of the gas are mixed, each of these being furnished with a
tube, and communicating with a long flexible pipe, which conveys the gas
into the balloon.

EMILY.

But the fire-balloons which were first invented, and have been since
abandoned, on account of their being so dangerous, were constructed,
I suppose, on a different principle.

MRS. B.

They were filled simply with atmospherical air, considerably rarefied by
heat; and the necessity of having a fire underneath the balloon, in
order to preserve the rarefaction of the air within it, was the
circumstance productive of so much danger.

If you are not yet tired of experiments, I have another to show you. It
consists in filling soap-bubbles with a mixture of hydrogen and oxygen
gases, in the proportions that form water; and afterwards setting fire
to them.

EMILY.

They will detonate, I suppose?

MRS. B.

Yes, they will. As you have seen the method of transferring the gas from
the receiver into the bladder, it is not necessary to repeat it. I have
therefore provided a bladder which contains a due proportion of oxygen
and hydrogen gases, and we have only to blow bubbles with it.

CAROLINE.

Here is a fine large bubble rising--shall I set fire to it with the
candle?

MRS. B.

If you please . . . .

CAROLINE.

Heavens, what an explosion! --It was like the report of a gun: I confess
it frightened me much. I never should have imagined it could be so loud.

EMILY.

And the flash was as vivid as lightning.

MRS. B.

The combination of the two gases takes place during that instant of time
that you see the flash, and hear the detonation.

EMILY.

This has a strong resemblance to thunder and lightning.

MRS. B.

These phenomena, however, are generally of an electrical nature. Yet
various meteorological effects may be attributed to accidental
detonations of hydrogen gas in the atmosphere; for nature abounds with
hydrogen: it constitutes a very