crawled into the long tube through which torpedoes were to be discharged
in war time.

One end of this torpedo tube projects slightly into the water, at the
bow of the submarine boat. The other end of the tube is well inside the
craft. Two doors, or "ports," as they are called, close the tube at the
ends. Ordinarily the forward port is closed, to keep water from
entering the boat. When a torpedo is placed in the tube for firing, the
outer or forward port is opened automatically just at the instant of
discharging the torpedo. Enough compressed air is turned into the tube
to force the torpedo out, after which the torpedo goes on its deadly
journey propelled by its own motor. The presence of the air thus turned
into the tube at the instant of firing keeps out the water until the
tube's forward port is once more closed. Then the rear port of the
tube, inside the submarine boat, may be opened whenever it is desired.

Captain Jack Benson, when he reached bottom with the "Pollard," and had
donned his bathing suit, crawled into the tube through the rear port.
This port was then closed. Hal Hastings simultaneously opened the
outer port and discharged compressed air into the tube. Thus Jack
forced his way out into the water, and, with the aid of his natural
buoyancy, made a quick swim for the surface.

In returning, he had dived down, close to the anchor cable. Nearer
the bottom he seized the cable, thus hauling himself down to the outer
port of the torpedo tube. He had quickly crawled into the tube, where
the presence of air still kept the water out. As he knocked heavily
at the rear port with both hands, Hal swiftly turned in a moderate
discharge of compressed air, while Eph, controlling mechanism inside,
swung the forward port shut. Then the rear port was swung back, Captain