"Look down on the top of the candle around the wick. See, it is a little cup full of melted wax. The heat of the flame has melted the 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 sharpshins?" "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 wax is all used up, and the candle is gone. So the flame, uncle, you see is the last of the candle, and the candle seems to go through the flame into nothing--although it doesn't, but goes into several things, and isn't it curious, as Professor Faraday said, that the candle should look so splendid and glorious in going away." "How well he remembers, doesn't he?" observed Mrs. Wilkinson. "I dare say," proceeded Harry, "that the flame of the candle looks flat to you; but if we were to put a lamp glass over it, so as to shelter it from the draught, you would see it is round, round sideways, and running up to a peak. It is drawn up by the hot air; you know that hot air always rises, and that is the way smoke is taken up the chimney. What should you think was in the middle of the flame?" "I should say, fire," replied Uncle Bagges. "Oh, no! The flame is hollow. The bright flame we see is something no thicker than a thin peel, or skin; and it doesn't touch the wick. Inside of it is the vapor I told you of just now. If you put one end of a bent pipe into the middle of the flame, and let the other end of the pipe dip into a bottle, the vapor or gas from the candle will mix with the air there; and if you set fire to the mixture of gas from the candle and air in the bottle, it would go off with a bang."