aving in the same manner combined with
some of the hydrogen of the water, the particles of oxygen that were
combined with it, are set free, and emitted in a gaseous form.

MRS. B.

Precisely so. But I should not forget to observe, that the wires used in
this experiment are made of platina, a metal which is not capable of
combining with oxygen; for otherwise the wire would combine with the
oxygen, and the hydrogen alone would be disengaged.

CAROLINE.

But could not water be decomposed without the electric circle being
completed? If, for instance, you immersed only the positive wire in the
water, would it not combine with the oxygen, and the hydrogen gas be
given out?

MRS. B.

No; for as you may recollect, the battery cannot act unless the circle
be completed; since the positive wire will not give out its electricity,
unless attracted by that of the negative wire.

CAROLINE.

I understand it now. --But look, Mrs. B., the decomposition of the water
which has now been going on for some time, does not sensibly diminish
its quantity--what is the reason of that?

MRS. B.

Because the quantity decomposed is so extremely small. If you compare
the density of water with that of the gases into which it is resolved,
you must be aware that a single drop of water is sufficient to produce
thousands of such small bubbles as those you now perceive.

CAROLINE.

But in this experiment, we obtain the oxygen and hydrogen gases mixed
together. Is there any means of procuring the two gases separately?

MRS. B.

They can be collected separately with great ease, by modifying a little
the experiment. Thus if instead of one tube, we employ two, as you see
here, (c, d, PLATE VIII. fig. 2.) both tubes being closed at one end,
and open at the other; and if after filling these tubes with water, we
place them standing in a glass of water (e), with their open end
downwards, you will see that the moment we connect the wires (a, b)
which proceed upwards from the interior of each tube, the one with one
end of the battery, and the other with the other end, the water in the
tubes will be decomposed; hydrogen will be given out round the wire in
the tube connected with the positive end of the battery, and oxygen in
the other; and these gases will be evolved, exactly in the proportions
which I have before mentioned, namely, two measures of hydrogen for one
of oxygen. We shall now begin the experiment, but it will be some time
before any se