to burn part of the Thames, or of any other
water; I mean the gas that I have just told
you about, which is called hydrogen. In
burning, hydrogen produces water again, like
the flame of the candle. Indeed, hydrogen is
that part of the water, formed by a candle
burning, that comes from the wax. All
things that have hydrogen in them produce
water in burning, 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.
Collect the bubbles from both wires in a tube,
and fire them, and they turn to water again;
and this water is exactly the same weight as
the quantity that has been changed into the
two gases. Now then, uncle, what should
you think water was composed of?"

"Eh. well—I suppose of those very
identical two gases, young gentleman."

"Eight, uncle. Recollect that the gas from
one of the wires was hydrogen, the one-ninth
of water. What should you guess the gas
from the other wire to be?"

"Stop—eh?—wait a bit—eh?—oh!—why,
the other eight-ninths, to be sure."

"Good again, uncle. Now this gas that is
eight-ninths of water is the gas called oxygen
that I mentioned just now. This is a very
curious gas. It won't burn in air at all
itself, like gas from a lamp, but it has a
wonderful power of making things burn that
are lighted and put into it. If you fill a jar
with it——"

"How do you manage that?" Mr. Bagges
inquired.

"You fill the jar with water," answered
Harry, "and you stand it upside down in a
vessel full of water too. Then you let bubbles
of the gas up into the jar and they turn out the
water and take its place. Put a stopper in
the neck of the jar, or hold a glass plate
against the mouth of it, and you can take it
out of the water and so have bottled oxygen.
A lighted candle put into a jar of oxygen
blazes up directly and is consumed before you
can say Jack Robinson. Charcoal burns
away in it as fast, with beautiful bright
sparks—phosphorus with a light that dazzles
you to look at—and a piece of iron or steel
just made red-hot at the end first, is burnt
in oxygen quicker than a stick would be in
common air. The experiment of burning
things in oxygen beats any fire-works."

"Oh, how jolly!" exclaimed Tom.

"Now we see, uncle," Harry continued,
"that water is hydrogen and oxygen united
together, that water is got wherever hydrogen
is burnt in common air, that a candle won't
burn without air, and that when a candle
burns there is hydrogen in it burning, and
forming water. Now, then, where does the
hydrogen of the candle get the oxygen from,
to turn into water with it!"

"From the air, eh?"

"Just so. I can't stop to tell you of the
other things which there is oxygen in, and the
many beautiful and amusing ways of getting it.
But as there is oxygen in the air, and as oxygen
makes things burn at such a rate, perhaps
you wonder why air does not make things
burn as fast as oxygen. The reason is, that
there is something else in the air that mixes
with the oxygen and weakens it."

"Makes a sort of gaseous grog of it,
eh?" said Mr. Bagges. "But how is that
proved?"

"Why, there is a gas, called nitrous gas,
which, if you mix it with oxygen, takes all the