[Two collodion balloons were inflated, and
sent up, one being held by a string.] Here is another larger one made of
thin membrane, which we will fill and allow to ascend. You will see they
will all remain floating about until the gas escapes.
What, then, are the comparative weights of these substances? I have a
table here which will shew you the proportion which their weights bear to
each other. I have taken a pint and a cubic foot as the measures, and have
placed opposite to them the respective figures. A pint measure of this
hydrogen weighs three-quarters of our smallest weight (a grain), and a
cubic foot weighs one-twelfth of an ounce; whereas a pint of water weighs
8,750 grains, and a cubic foot of water weighs almost 1,000 ounces. You
see, therefore, what a vast difference there is between the weight of a
cubic foot of water and a cubic foot of hydrogen.
Hydrogen gives rise to no substance that can become solid, either during
combustion or afterwards as a product of its combustion. But when it
burns, it produces water only; and if we take a cold glass and put it over
the flame, it becomes damp, and you have water, produced immediately in
appreciable quantity; and nothing is produced by its combustion but the
same water which you have seen the flame of the candle produce.
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