and six hours off.
That's what we call a trick--the six hours on, I mean. So you will have
every other six hours to rest, or do anything you like; that is, after
you have attended to the horses."

"Horses!" repeated James, puzzled; for the animals attached to the boat
at that moment were mules.

"Some of our horses are mules," said Captain Letcher, smiling.
"However, it makes no difference. You will have to feed and rub them
down, and then you can lie down in your bunk, or do anything else you
like."

"That won't be very hard work," said James, cheerfully.

"Oh, I forgot to say that you can ride or walk, as you choose. You can
rest yourself by changing from one to the other."

James thought he should like to ride on horseback, as most boys do. It
was not, however, so good fun as he anticipated. A canal-boat horse is
by no means a fiery or spirited creature. His usual gait is from two to
two and a half miles an hour, and to a boy of quick, active temperament
the slowness must be rather exasperating. Yet, in the course of a day a
boat went a considerable distance. It usually made fifty, and sometimes
sixty miles a day. The rate depended on the number of locks it had to
pass through.

Probably most of my young readers understand the nature of a lock. As
all water seeks a level, there would be danger in an uneven country that
some parts of the canal would be left entirely dry, and in others the
water would overflow. For this reason at intervals locks are
constructed, composed of brief sections of the canal barricaded at each
end by gates. When a boat is going down, the near gates are thrown open
and the boat enters the lock, the water rushing in till a level is
secured; then the upper gates are closed, fastening the boat in the
lock. Next the lower gates are opened, the water in the lock seeks the
lower level of the other section of the canal, and the boat moves out of
the lock, the water subsiding gradually beneath it. Next, the lower
gates are closed, and the boat proceeds on its way. It will easily be
understood, when the case is reversed, and the boat is going up, how
after being admitted into the lock it will be lifted up to the higher
level when the upper gates are thrown open.

If any of my young readers find it difficult to understand my
explanation, I advise them to read Jacob Abbot's excellent book, "Rollo
on the Erie Canal," where the whole matter is lucidly explained.

Railroads were not at that time a