and the more there is in
them, the more they produce. When pure hydrogen burns, nothing comes
from it but water, no smoke or soot at all. If you were to burn one
ounce of it, the water you would get would be just nine ounces. There
are many ways of making hydrogen, besides out of steam by the hot
gun-barrel. I could show it you in a moment by pouring a little
sulphuric acid mixed with water into a bottle upon a few zinc or steel
filings, and putting a cork in the bottle with a little pipe through it,
and setting fire to the gas that would come from the mouth of the pipe.
We should find the flame very hot, but having scarcely any brightness. I
should like you to see the curious qualities of hydrogen, particularly
how light it is, so as to carry things up in the air; and I wish I had
a small balloon to fill with it and make go up to the ceiling, or a
bag-pipe full of it to blow soap-bubbles with, and show how much faster
they rise than common ones, blown with the breath."

"So do I," interposed Master Tom.

"And so," resumed Harry, "hydrogen, you know, uncle, is part of water,
and just one-ninth part."

"As hydrogen is to water, so is a tailor to an ordinary individual, eh?"
Mr. Bagges remarked.

"Well, now, then, uncle, if hydrogen is the tailor's part of the water,
what are the other eight parts? The iron-turnings used to make hydrogen
in the gun-barrel, and rusted, take just those eight parts from the
water in the shape of steam, and are so much the heavier. Burn iron
turnings in the air, and they make the same rust, and gain just the same
in weight. So the other eight parts must be found in the air for one
thing, and in the rusted iron turnings for another, and they must also
be in the water; and now the question is, how to get at them?"

"Out of the water? Fish for them, I should say," suggested Mr. Bagges.

"Why, so we can," said Harry. "Only instead of hooks and lines, we must
use wires--two wires, one from one end, the other from the other, of a
galvanic battery. Put the points of these wires into water, a little
distance apart, and they instantly take the water to pieces. If they are
of copper, or a metal that will rust easily, one of them begins to rust,
and air-bubbles come up from the other. These bubbles are hydrogen. The
other part of the water mixes with the end of the wire and makes rust.
But if the wires are of gold, or a metal that does not rust easily,
air-bubbles rise from the ends of both wires.