llected a force of trawlers and destroyers, and the
submarine was hunted for fourteen hours by this force, assisted by the
airship. During this period she succeeded in sinking one of the German
destroyers, and was eventually left unmolested.

For a correct appreciation of submarine warfare it is necessary to have
a clear idea of the characteristics and qualities of the submarine
herself, of the numbers possessed by the enemy, and of the rate at which
they were being produced. It is also necessary, in order to understand
the difficulty of introducing the counter measures adopted by the Royal
Navy, to know the length of time required to produce the vessels and the
weapons which were employed or which it was intended to employ in the
anti-submarine war.

The German submarines may be divided into four classes, viz.: Submarine
cruisers, U-boats, U.B.-boats, U.C.-boats. There were several variations
of each class.

The earlier _submarine cruisers_ of the "Deutschland" class were
double-hulled vessels, with a surface displacement of 1,850 tons, and
were about 215 feet long; they had a surface speed of about 12 knots and
a submerged speed of about 6 knots. They carried two 5.9-inch guns, two
22 pounders, two torpedo tubes, and 12 torpedoes. They could keep the
sea for quite four months without being dependent on a supply ship or
base.

The later _submarine cruisers_ were double-hulled, 275-320 feet long,
had a surface speed of 16-18 knots, and a submerged speed of about 7 to
8 knots. They carried either one or two 5.9-inch guns, six torpedo
tubes, and about 10 torpedoes. They had a very large radius of action,
viz., from 12,000 to 20,000 miles, at a speed of 6 knots. A large number
(some 30 to 40) of these boats were under construction at the time of
the Armistice, but very few had been completed.

There were two or three types of _U-boats_. The earlier vessels were 210
to 220 feet long, double-hulled, with a surface displacement of about
750 tons, a surface speed of 15 to 16 knots, and a submerged speed of
about 8 knots. They carried one or two 4.1-inch guns, four to six
torpedo tubes, and about 10 torpedoes.

Later vessels of the class were 230 to 240 feet long, and of 800 to 820
tons surface displacement, and carried six torpedo tubes and 16
torpedoes. Some of them, fitted as minelayers, carried 36 mines, and two
torpedo tubes, but only two torpedoes. A later and much larger class of
minelayers carried a 5.9-inch gun,