With all that I have nothing to do in this book, but I hope you
will pardon just a little reference to the Canal, especially the
lock features, since Joe and Blake had a part in at least filming
those wonderful structures.

You know there are two kinds of canals, those on the level, which
are merely big over-grown ditches, and those which have to go over
hills and through low valleys.

There are two ways of getting a canal over a hill. One is to build
it and let the water in to the foot of the hill, and then to raise
vessels over, the crest of the hill, and down the other side to
where the canal again starts, by means of inclined planes, or
marine railways.

The other method is by "locks," as they are called. That is, there
are built a series of basins with powerful, water-tight gates
dividing them. Boys who live along canals well know how locks
work.

A boat comes along until it reaches the place where the lock is.
It is floated into a basin, or section, of the waterway, and a
gate is closed behind it. Then, from that part of the canal which
is higher than that part where the boat then is, water is admitted
into the basin, until the boat rises to the level of the higher
part of the canal. Then the higher gate is opened, and the vessel
floats out on the higher level. It goes "up hill," so to speak.

By reversing the process it can also go "down hill." Of course
there must be heavy gates to prevent the higher level waters from
rushing into those of the lower level.

Some parts of the Panama Canal are eighty-five feet higher than
other parts. In other words, a vessel entering the Canal at Colon,
on the Atlantic side of the Isthmus, must rise eighty-five feet to
get to the level of Gatun Lake, which forms a large part of the
Canal. Then, when the Pacific end is approached, the vessel must
go down eighty-five feet again, first in one step of thirty and a
third feet, and then in two steps, or locks, aggregating
fifty-four and two-thirds feet. So you see the series of locks at
either end of the great Canal exactly balance one another, the
distance at each end being eighty-five feet.

It is just like going up stairs at one end of a long board walk
and down again at the other end, only the steps are of water, and
not wood.

The tug bearing Blake, Joe and Mr. Alcando was now steaming over
toward Toro Point break-water, which I have before alluded to.
This was built to make a good harbor at Colon, where violent
stor