It was not really a hoop, it was a _tire_. It was
made of a much larger and thicker bar of iron, than those which are
used for hoops. It was a tire belonging to a wheel. The wheel was
lying upon the ground near, ready to receive the tire. It was the hind
wheel of a wagon. The wagon itself was standing in front of the shop,
with one end of the hind axletree supported by a block.
"What do they heat the tire for?" asked Marco.
"To swell it," replied Forester. "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.
