sistance of blowing, from the lightness of the
gas. --Will you mix some soap and water whilst I fill this bladder with
the gas contained in the receiver which stands on the shelf in the
water-bath?

CAROLINE.

What is the use of the brass-stopper and turn-cock at the top of the
receiver?

MRS. B.

It is to afford a passage to the gas when required. There is, you see,
a similar stop-cock fastened to this bladder, which is made to fit that
on the receiver. I screw them one on the other, and now turn the two
cocks, to open a communication between the receiver and the bladder;
then, by sliding the receiver off the shelf, and gently sinking it into
the bath, the water rises in the receiver and forces the gas into the
bladder. (PLATE IX. fig. 1.)

[Illustration: Plate IX. Vol. I. p. 228

Fig. 1. Apparatus for transferring gases from a Receiver into a
bladder.
Fig. 2. Apparatus for blowing Soap bubbles.]

CAROLINE.

Yes, I see the bladder swell as the water rises in the receiver.

MRS. B.

I think that we have already a sufficient quantity in the bladder for
our purpose; we must be careful to stop both the cocks before we
separate the bladder from the receiver, lest the gas should escape.
--Now I must fix a pipe to the stopper of the bladder, and by dipping
its mouth into the soap and water, take up a few drops--then I again
turn the cock, and squeeze the bladder in order to force the gas into
the soap and water at the mouth of the pipe. (PLATE IX. fig. 2.)

EMILY.

There is a bubble--but it bursts before it leaves the mouth of the pipe.

MRS. B.

We must have patience and try again; it is not so easy to blow bubbles
by means of a bladder, as simply with the breath.

CAROLINE.

Perhaps there is not soap enough in the water; I should have had warm
water, it would have dissolved the soap better.

EMILY.

Does not some of the gas escape between the bladder and the pipe?

MRS. B.

No, they are perfectly air tight; we shall succeed presently, I dare
say.

CAROLINE.

Now a bubble ascends; it moves with the rapidity of a balloon. How
beautifully it refracts the light!

EMILY.

It has burst against the ceiling--you succeed now wonderfully; but why
do they all ascend and burst against the ceiling?

MRS. B.

Hydrogen gas is so much lighter than atmospherical air, that it ascends
rapidly with its very light envelope, which is burst by the force with
which it strikes the ceiling.

Air-ba