ss the street toward the fire. Marco saw that
there was a large blacksmith's shop there. It was a very neat-looking
building, painted red. There was a large door in the front, and a very
low window, with a shutter hanging over it, by the side of the door.
In an open yard, by the side of the shop, was the fire. The fire was
in the form of a ring. There were several men standing about it; one
of them, whom Marco supposed was the blacksmith, by his leather apron,
was putting on small sticks of wood and chips, here and there, around
the ring. Marco saw that there was a large iron hoop, as he called it,
on the fire. 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.

"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."