skipper went below.

"We'll swing in one of the dummy torpedoes, first, of course," announced
Mr. Danvers.

One of the dummies was, therefore, hauled forward on a truck, then
forced on into the torpedo tube. Jack watched, intently, this part of
the business.

The torpedo itself was a cigar-shaped affair, with a propeller at the
after end. This propeller was set in motion by means of an engine in
the after part of the torpedo, the engine being so constructed that it
was set in operation at the moment the torpedo left the tube and entered
the ocean outside. The propeller was fitted with apparatus that would
drive the torpedo in a straight line.

"The torpedo looks like a miniature submarine, doesn't it?" muttered
young Benson.

"It surely does," nodded the naval officer. "And, since the torpedo has
to travel under water, what better model could have been chosen? Now,
the engines in these dummy torpedoes can be set for two, four, six or
eight hundred yards, and the torpedo, once it enters the water, travels
forward, in a straight line until the engine gives out. That is, the
torpedo travels ahead if it doesn't hit something. So, in actual war
conditions, we would always get nearer to the object than the distance
for which the engine is set to run. The speed of a torpedo like this,
under water, is a good deal better than thirty miles an hour, but the
distance the torpedo can go is naturally short. That is a direct
consequence of its speed. Now, Mr. Benson, would you like to know how