It is so light that it carries things up:
it is far lighter than the atmosphere; and I dare say I can shew you this
by an experiment which, if you are very clever, some of you may even have
skill enough to repeat. Here is our generator of hydrogen, and here are
some soap-suds. I have an india-rubber tube connected with the hydrogen
generator, and at the end of the tube is a tobacco-pipe.
[Illustration: Fig. 18.]
I can thus put the pipe into the suds, and blow bubbles by means of the
hydrogen. You observe how the bubbles fall downwards when I blow them with
my warm breath; but notice the difference when I blow them with hydrogen.
[The Lecturer here blew bubbles with hydrogen, which rose to the roof of
the theatre.] It shews you how light this gas must be in order to carry
with it not merely the ordinary soap-bubble, but the larger portion of a
drop hanging to the bottom of it. I can shew its lightness in a better way
than this; larger bubbles than these may be so lifted up; indeed, in
former times balloons used to be filled with this gas. Mr. Anderson will
fasten this tube on to our generator, and we shall have a stream of
hydrogen here with which we can charge this balloon made of collodion. I
need not even be very careful to get all the air out, for I know the power
of this gas to carry it up.
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