r said. "Well, now we'll start."

If either Blake or Joe felt any surprise over the hurried visit,
at the last minute, of Mr. Alcando's friend, they said nothing to
each other about it. Besides, they had other matters to think of
just then, since now their real moving picture work was about to
begin.

In a short time they were moving away from the pier, up the harbor
and toward the wonderful locks and dam that form the amazing
features (aside from the Culebra Cut) of the great Canal.

"Better get our cameras ready; hadn't we, Blake?" suggested Joe.

"I think so," agreed his chum. "Now, Mr. Alcando, if you want to
pick up any points, you can watch us. A little later we'll let you
grind the crank yourself."

I might explain, briefly, that moving pictures are taken not by
pressing a switch, or a rubber bulb, such as that which works a
camera shutter, but by the continuous action of a crank, or
handle, attached to the camera. Pressing a bulb does well enough
for taking a single picture, but when a series, on a long
celluloid strip, are needed, as in the case for the "movies," an
entirely different arrangement becomes absolutely necessary.

The sensitive celluloid film must move continuously, in a somewhat
jerky fashion, inside the dark light-tight camera, and behind the
lens. As each picture, showing some particular motion, is taken,
the film halts for the briefest space of time, and then goes on,
to be wound up in the box, and a new portion brought before the
lens for exposure.

All this the crank does automatically, opening and closing the
shutter, moving the film and all that is necessary.

I wish I had space, not only to tell you more of how moving
pictures are made, but much about the Panama Canal. As to the
former--the pictures--in other books of this series I have done
my best to give you a brief account of that wonderful industry.

Now as to the Canal--it is such a vast undertaking and subject
that only in a great volume could I hope to do it justice. And in
a story (such as this is intended to be), I am afraid you would
think I was trying to give you pretty dry reading if I gave you
too many facts and figures.

Of course many of you have read of the Canal in the
newspapers--the controversy over the choice of the route, the
discussion as to whether a sea level or a lock canal was best, and
many other points, especially whether the Gatun Dam would be able
to hold back the waters of the Chagres River.