ive into its friendly depths, complete
their work, and make for the parent ship.

Low-lying sea-fogs are favourable to aerial raids provided the scout is
able to catch sight of the upper parts of landmarks to enable him to
be sure of the correctness of his line of flight-in cases where
the distance is very short compass direction is sufficiently
reliable-because the bank of vapour not only constitutes a perfect
screen, but serves as a blanket to the motor exhaust, if not completely,
at least sufficiently to mislead those below. Fogs, as every mariner
will testify, play strange tricks with the transmission of sound. Hence,
although those on the vessels below might detect a slight hum, it might
possibly be so faint as to convey the impression that the aviator was
miles away, when, as a matter of fact, he was directly overhead. This
confusion arising from sound aberration is a useful protection in
itself, as it tends to lure a naval force lying in or moving through the
fog into a false sense of security.

The development of the submarine revealed the incontrovertible fact
that this arm would play a prominent part in future operations upon the
water: a presage which has been adequately fulfilled during the
present conflict. The instinct of self-preservation at once provoked
a discussion of the most effective ways and means of disguising its
whereabouts when it travels submerged. To this end the German naval
authorities conducted a series of elaborate and interesting experiments
off the island of Heligoland. As is well known, when one is directly
above a stretch of shallow water, the bottom of the latter can be seen
quite distinctly. Consequently, it was decided to employ aerial craft
as detectives. Both the aeroplane and the dirigible took part in these
experiments, being flown at varying heights, while the submarine was
maneouvred at different depths immediately below. The sum of these
investigations proved conclusively that a submarine may be detected from
aloft when moving at a depth of from 30 to 40 feet. The outline of the
submerged craft is certainly somewhat blurred, but nevertheless it is
sufficiently distinct to enable its identity to be determined really
against the background or bottom of the sea. To combat this detection
from an aerial position it will be necessary inter alia to evolve a
more harmonious or protective colour-scheme for the submarine. Their
investigations were responsible for the inauguration of