s impossible to
follow from the low point of vantage of a periscope, for the
different formations of ships mean nothing to the submersible
commander. He is so placed that his range of vision is extremely
limited, and, on account of the low speed of his boat while submerged,
he can operate over only a very limited area of water while the other
vessels are moving many miles. Then, too, he is extremely vulnerable
to the effect of enemy shells and to the ramming of enemy ships. Under
these conditions the submersible commander is more or less forced to a
policy of lying ambushed to surprise his enemy. It is said that the
"Lusitania" was decoyed into a nest of submersibles. There was but
little chance of torpedoing her in any other way. There is also the
statement that Admiral Beatty passed with his battle-cruisers through
a flotilla of enemy submersibles without being touched.

Submersibles cannot attack their target in definite formations as do
surface vessels, and therefore they cannot operate in numbers with the
same effectiveness as do the latter. They must maneuver more or less
singly, and at random. Being limited to the torpedo, which, when they
are submerged, is their sole weapon of attack, they have an uncertain
means of striking their armed enemy. The eccentricities of the
automobile torpedo are well known; but, even eliminating the fact that
this missile is unreliable, the important question of accuracy in the
estimate of range and speed which the submersible commander has to
make before firing the torpedo must be considered. There is usually a
large percentage of error in his calculations unless the submersible
is extremely close to its target. Realizing these limitations, the
German submersibles are equipped with small torpedoes, which are
generally fired at ranges not exceeding eight hundred to two thousand
yards. The necessity of approaching the target so closely is, of
course, a tremendous handicap in the general operation of these boats.
In view of these facts, it is not surprising that the submersible
should not have been able to sweep the capital ship from the seas, as
was predicted by certain experts before the war.

II

Admiral Sir Cyprian Bridge regards the functions of defense by a navy
as divisible into three main classifications. He says, "The
above-mentioned three divisions are called in common speech, coast
defense, colonial defense, and defense of commerce." From this
classification we are gi