"It is necessary to have the tire go
on very tight, so as to hold the wheel together with all the force of
the iron. Now when iron is heated it swells, and then shrinks again
when it cools. So they heat the tire hot, and put it upon the wheel in
that state. Then when it cools it shrinks, and binds the whole wheel
together with a very strong grip."
"But if they put it on hot, it will burn the wood," said Marco.
"Yes," replied Forester, "it will burn the wood a little. They can not
help that entirely; but they stand ready with water, to pour on, as
soon as the tire is in its place, and so cool it immediately, so that
it does not burn the fellies enough to injure them."
"What are the fellies?" asked Marco.
"They are the parts of the wooden rim of the wheel. The rim is made of
several pieces of wood, which are called fellies."
So Forester took Marco to the wheel, and showed him the parts of
which the rim was composed. While Marco was looking at the wheel, the
blacksmith began to push away the burning brands a little from the
tire, as it began to be hot enough. Presently he went into his shop
and brought out several pairs of tongs. With these the men lifted the
tire out of the fire, but the blacksmith said it was a little too hot,
and he must let it cool a minute or two.
"Why, if it's very hot," said Marco, "it will grip the wheel all the
harder."
"It will grip it _too_ hard," said Forester. "Sometimes a tire
shrinks so much as to spring the spokes out of shape. Didn't you ever
see a wheel with the spokes bent out of shape?"
"I don't know," said Marco. "I never noticed wheels much."
"They do get bent, sometimes," said Forester. "It requires great care
to put on a tire in such a manner, as to give it just the right degree
of force to bind the wheel strongly together, without straining it."
[Illustration: THE TIRE.]
As soon as the tire became of the right temperature, the men took it
up again with the pairs of tongs - taking hold with them at different
sides of it - and then they put it down carefully over the wheel. The
wheel immediately began to smoke on all sides. In one or two places
it burst into a flame. The blacksmith, however, paid no attention to
this, but with a hammer, which he held in his hand, he knocked it down
into its place, all around the rim; then he took up a brown pitcher
full of water, which was standing near, and began to pour the
water on, walking round and round the wheel as he did it, so as to
extinguish the flames in every part and cool the iron.
