in a trench when a "Taube" is
overhead suffices to cause the trench to be blown to fragments, and time
after time the British soldiers have had to lie prone in their trenches
and suffer partial burial as an alternative to being riddled by
shrapnel.

The method of ascertaining the range of the target from the indications
given by the aeroplane are of the simplest character. The German method
is for the aerial craft to fly over the position, and when in vertical
line therewith to discharge a handful of tinsel, which, in falling,
glitters in the sunlight, or to launch a smoking missile which answers
the same purpose as a projectile provided with a tracer. This smoke-ball
being dropped over the position leaves a trail of black or whitish smoke
according to the climatic conditions which prevail, the object being to
enable the signal to be picked up with the greatest facility. The height
at which the aerial craft is flying being known, a little triangulation
upon the part of the observer at the firing point enables him to
calculate the range and to have the guns laid accordingly.

When the aerial craft has been entrusted with the especial duty of
directing artillery-fire, a system of communication between the aerial
observer and the officer in charge of the artillery is established,
conducted, of course, by code. In the British Army, signalling is both
visual and audible. In daylight visual signalling is carried out by
means of coloured flags or streamers and smoke-signals, while audible
communication is effected by means of a powerful horn working upon the
siren principle and similar to those used by automobiles. Both flags and
sound-signals, however, are restricted owing to the comparatively short
distances over which they can be read with any degree of accuracy. The
smoke-signal therefore appears to be the most satisfactory and reliable,
as the German airmen have proved conclusively, for the simple reason
that the trail of smoke may be picked up with comparative ease, even
at a distance, by means of field glasses. The tinsel too, is readily
distinguishable, particularly in bright weather, for the glittering
surface, catching the sun-light, acts some what in the manner of a
heliograph.

The progress of the airman is followed by two officers at the base from
which he started. One is equipped with the director, while the
second takes the range. Directly this has been found as a result of
calculation, the guns are laid rea