a kind of wire gauze. You will observe that this vessel is a porous thing;
for if I pour a little water on to the top, it will run out at the bottom.
You would be puzzled for a good while if I asked you what the state of
this vessel is, what is inside it, and why it is there? The vessel is full
of water, and yet you see the water goes in and runs out as if it were
empty. In order to prove this to you, I have only to empty it. The reason
is this,--the wire, being once wetted, remains wet; the meshes are so
small that the fluid is attracted so strongly from the one side to the
other, as to remain in the vessel although it is porous. In like manner
the particles of melted tallow ascend the cotton and get to the top; other
particles then follow by their mutual attraction for each other, and as
they reach the flame they are gradually burned.

Here is another application of the same principle. You see this bit of
cane. I have seen boys about the streets, who are very anxious to appear
like men, take a piece of cane, and light it and smoke it, as an imitation
of a cigar. They are enabled to do so by the permeability of the cane in
one direction, and by its capillarity. If I place this piece of cane on a
plate containing some camphin (which is very much like paraffin in its
general character), exactly in the same manner as the blue fluid rose
through the salt will this fluid rise through the piece of cane. There
being no pores at the side, the fluid cannot go in that direction, but
must pass through its length. Already the fluid is at the top of the cane:
now I can light it and make it serve as a candle. The fluid has risen by
the capillary attraction of the piece of cane, just as it does through the
cotton in the candle.

Now, the only reason why the candle does not burn all down the side of the
wick is, that the melted tallow extinguishes the flame. You know that a
candle, if turned upside down, so as to allow the fuel to run upon the