ay, which is flashed in Morse code on the
navigation lights by the aviator when ready to leave the ground; he then
awaits an answer from the directing stand. Simultaneously with the
lighting up of the huge "landing T," the letter flashed from the first
machine ready is repeated by the signal officer. The answer received,
the machine taxies across the aerodrome to the starting-point, turns,
hurtles down the flare-path and leaves the ground at the head of the
"T." Under this simple method of direction I have seen twenty aeroplanes
leave an aerodrome on a pitch-black night in twelve minutes without a
single mishap.

On leaving the ground the aeroplanes fly dead into the wind for a couple
of miles, circle back to the left around the aerodrome, and head into
the wind again until the height at which the flight is to be carried out
is reached. The first aeroplane to reach this height passes directly
over the aerodrome and then steers a course to the first lighthouse. A
comparison of this course with the previously figured course, and a
comparison of the previously calculated ground speed with the time taken
to travel from the aerodrome to the lighthouse enables the aviators, by
the use of instruments and a few simple calculations, to gauge their
drift. This process is continued on another course to the next
lighthouse and the previously tested direction and velocity of wind are
accurately checked in this way and future courses altered accordingly.
These calculations are all important to the long-distance night bomber,
for although roads show up in the moonlight like white threads, they are
too numerous and interwoven to be followed for great distances, and
although rivers and lakes look like silver ribbons and blotches, the
moon may be obscured at any moment or the ground itself may be
obliterated by low clouds or mist. Accuracy in aerial navigation,
therefore, is of the utmost importance in long-distance night flying.

The night aviator, however, has many things to think of besides a
constant checking and readjustment of his course according to variations
in direction and velocity of wind. On his own side of the lines he is
constantly challenged by searchlights which must be answered immediately
if the aviator wishes to avoid the risk of being shot down by his own
anti-aircraft guns or of being attacked by his own night-patrol
machines. The method of answering these challenges is extremely simple.
All that is required of the