is all this gas procured in such large quantities?

MRS. B.

It is obtained from coal, by distillation. --Coal, when exposed to heat
in a close vessel, is decomposed; and hydrogen, which is one of its
constituents, rises in the state of gas, combined with another of its
component parts, carbon, forming a compound gas, called _Hydrocarbonat_,
the nature of which we shall again have an opportunity of noticing when
we treat of carbon. This gas, like hydrogen, is perfectly transparent,
invisible, and highly inflammable; and in burning it emits that vivid
light which you have so often observed.

CAROLINE.

And does the process for procuring it require nothing but heating the
coals, and conveying the gas through tubes?

MRS. B.

Nothing else; except that the gas must be made to pass, immediately at
its formation, through two or three large vessels of water, in which it
deposits some other ingredients, and especially water, tar, and oil,
which also arise from the distillation of coals. The gas-light
apparatus, therefore, consists simply in a large iron vessel, in which
the coals are exposed to the heat of a furnace,--some reservoirs of
water, in which the gas deposits its impurities,--and tubes that convey
it to the desired spot, being propelled with uniform velocity through
the tubes by means of a certain degree of pressure which is made upon
the reservoir.

EMILY.

What an admirable contrivance! Do you not think, Mrs. B., that it will
soon get into universal use?

MRS. B.

Most probably, as to the lighting of streets, offices, and public
places, as it far surpasses any former invention for that purpose; but
as to the interior of private houses, this mode of lighting has not yet
been sufficiently tried to know whether it will be found generally
desirable, either in regard to economy or convenience. It may, however,
be considered as one of the happiest applications of chemistry to the
comforts of life; and there is every reason to suppose that it will
answer the full extent of public, expectation.

I have another experiment to show you with hydrogen gas, which I think
will entertain you. Have you ever blown bubbles with soap and water?

EMILY.

Yes, often, when I was a child; and I used to make them float in the air
by blowing them upwards.

MRS. B.

We shall fill some such bubbles with hydrogen gas, instead of
atmospheric air, and you will see with what ease and rapidity they will
ascend, without the as