wax just round the wick. The cold air keeps the outside of it hard,
so as to make the rim of it. The melted wax in the little cup goes up
through the wick to be burnt, just as oil does in the wick of a lamp.
What do you think makes it go up, uncle?"

"Why--why, the flame draws it up, doesn't it?"

"Not exactly, uncle. It goes up through little tiny passages in the
cotton wick, because very, very small channels, or pipes, or pores,
have the power in themselves of sucking up liquids. What they do it by
is called cap--something."

"Capillary attraction, Harry," suggested Mr. Wilkinson.

"Yes, that's it; just as a sponge sucks up water, or a bit of
lump-sugar the little drop of tea or coffee left in the bottom of a
cup. But I mustn't say much more about this, or else you will tell me
I am doing something very much like teaching my grandmother to--you
know what."

"Your grandmother, eh, young sharp-shins?"

"No--I mean my uncle. Now, I'll blow the candle out, like Moses; not
to be in the dark, though, but to see into what it is. Look at the
smoke rising from the wick. I'll hold a bit of lighted paper in the
smoke, so as not to touch the wick. But see, for all that, the candle
lights again. So this shows that the melted wax sucked up through
the wick is turned into vapor; and the vapor burns. The heat of the
burning vapor keeps on melting more wax, and that is sucked up too
within the flame, and turned into vapor, and burnt, and so on till the