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."

"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.