them.
4.26 p.m. Hit. Hit. Hit.
4.32 p.m. About 50 yards short and to the right.
4.37 p.m. Your last shot in the middle of 3 batteries in action;
search all round within 300 yards of your last
shot and you have them.
4.42 p.m. I am coming home now.

The later signals directing artillery fire were not so full of colour
as these early messages. They consisted of code letters. The clock code
for signalling the results of artillery fire was first used in 1915 and
afterwards generally throughout the war. The target was taken as the
centre of a clock and imaginary lines were circumscribed around it at
distances of 10, 25, 50, 100, 200, 300, 400, and 500 yards. These lines
were lettered Y, Z, A, B, C, D, E, F, respectively. Twelve o'clock was
always taken as true north from the target and the remaining hours
accordingly. An observer noted the fall of the rounds with reference to
the imaginary circles and clock-hours and signalled the result, for
instance, as Y 4, or C 6. A direct hit was O.K, and there were other
signals. Messages from the battery or any other ground station were
signalled to the observer in the aeroplane by means of white strips
which were laid out on the ground to form the letters of a code.

During the battle of the Aisne, the wireless machines were few in number
and other methods of signalling were mostly in use. On the 15th of
September Captain L. E. O. Charlton fired Very lights over enemy guns
previously observed. On the 24th of September 'Lieutenant Allen and two
others with aeroplanes indicated targets and observed fire,
communication being by flash signals'. Sometimes the pilots returned and
landed to report on gun positions. But when once the gunners had
profited by the superior accuracy and speed of report by wireless, they
were hungry for more machines. On the 23rd of September the commander of
the Second Corps telegraphed to General Headquarters: 'I hope that you
will be able to spare the wireless aeroplane and receiving set to Third
Division again to-morrow. The results were so good yesterday that it
seems a pity not to keep it with the Division, which has got accustomed
to its uses and is in a position to benefit even more largely by the
experience gained.' The answer was that the machine had been damaged by
anti-aircraft fire, but would be ready again shortly. A wireless
aeroplane was as popular as an opera-singer, and the headquarters
wireless section s