hen you put it on. There are ways of collecting this sort of
dew, and when it is collected it turns out to be really water. I am not
joking, uncle. Water is one of the things which the candle turns into in
burning--water, coming out of fire. A jet of oil gives above a pint of
water in burning. In some lighthouses they burn, Professor Faraday says,
up to two gallons of oil in a night, and if the windows are cold, the
steam from the oil clouds the inside of the windows, and, in frosty
weather, freezes into ice."

"Water out of a candle, eh?" exclaimed Mr. Bagges. "As hard to get, I
should have thought, as blood out of a post. Where does it come from?"

"Part from the wax, and part from the air, and yet not a drop of it
comes either from the air or the wax. What do you make of that, uncle?"

"Eh? Oh! I'm no hand at riddles. Give it up."

"No riddle at all, uncle. The part that comes from the wax isn't water,
and the part that comes from the air isn't water, but when put together
they become water. Water is a mixture of two things, then. This can be
shown. Put some iron wire or turnings into a gun-barrel open at both
ends. Heat the middle of the barrel red-hot in a little furnace. Keep
the heat up, and send the steam of boiling water through the red-hot
gun-barrel. What will come out at the other end of the barrel won't be
steam; it will be gas, which doesn't turn to water again when it gets
cold, and which burns if you put a light to it. Take the turnings out of
the gun-barrel, and you will find them changed to rust, and heavier than
when they were put in. Part of the water is the gas that comes out of
the barrel, the other part is what mixes with the iron turnings, and
changes them to rust, and makes them heavier. You can fill a bladder
with the gas that comes out of the gun-barrel, or you can pass bubbles
of it up into a jar of water turned upside down in a trough, and, as I
said, you can make this part of the water burn."

"Eh?" cried Mr. Bagges. "Upon my word. One of these days, we shall have
you setting the Thames on fire."

"Nothing more easy," said Harry, "than to burn part of the Thames, or
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,