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."

"Right, 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 t