? No. Why?" inquired Blake.

"Well, I happen to need some San Francisco street scenes for one of the
dramas," went on the theatrical man; "and it occurred to me that you
could get them when you weren't busy."

"Of course we could," answered Joe. "We can take the automatic, and set
it up wherever you say, and go looking for that shipping agent. When we
come back we'll have all the pictures we need."

"Good!" exclaimed Mr. Ringold. "Try that, if you don't mind. Get some
scenes down in the financial district, and others in the residential
section. Then, as long as you have to go to the shipping offices, get
some there."

The boys promised they would, and added the small but compact automatic
camera to their luggage as they started off.

This camera worked by compressed air. There was a small motor inside,
operated by a cylinder of air that could be filled by an ordinary
bicycle pump. Otherwise it was just like the other moving picture
cameras.

There was the upper box, in which was wound the unexposed reel of film.
From this it went over a roller, and the cog wheel, which engaged in the
perforations, thence down by means of the "gate," behind the lens and
shutter. There two claws reached up and grasped the film as the motor
operated, pulling down three-quarters of an inch each time, to be
exposed as the shutter was automatically opened in front of the lens.

Each one of the thousands of moving pictures, as I have explained in
previous books, is three-quarters of an inch deep, though, of course, on
the screen it is enormously enlarged.

After the film has been exposed, three-quarters of an inch at a time, it
goes below into another light-tight box of the camera, whence it is
removed to be developed and printed. The movement of the film, the
operation of the claws and the opening and closing of the shutter,
making it possible to take sixteen pictures a second, was, in this
camera, all controlled by the air motor.

Joe and Blake found much to amuse them in San Francisco, which they had
never before visited. They were a bit "green," but after their
experiences in New York they had no trouble in finding their way around.

"We'd better go to some hotel, or boarding house," suggested Joe, after
their arrival. "Pick out one where we can leave the camera working while
we're gone."

They did this, being fortunate enough to secure rooms in a good, though
not expensive, hotel near the financial district. One of their wind