at they were in front of the German position. German
cavalry patrolled the road in front of them, and they were under heavy
shell-fire from the British. They swam the Aisne, dried their clothes in
a house by the canal, and then walked to the British guns, which were
still in action. They were given food by the Third Cavalry Brigade, and
were taken back on a supply column to rejoin their squadron after an
absence of more than two days. It might be supposed that their troubles
were now at an end, but they had yet to face their squadron commander,
Major Burke, who sternly rebuked them for violating the order that no
two pilots should fly together in the same machine.

The work of observation now entered a new phase. When armies are in
fixed positions movement behind the front and along the lines of
communication does not greatly vary from day to day. The Flying Corps
were employed to map out the enemy's chief railheads, his aerodromes
(which were surprisingly numerous), his camps, and his dumps. They began
also to observe the positions of enemy batteries in order to range them
for our own artillery, and they made some attempts to take photographs
from the air of the enemy trenches and lines of communication.

Maubeuge had fallen on the 7th of September and, in addition to the
Seventh Reserve Corps and other troops, the siege artillery which had
been used to reduce Maubeuge was brought down to the Aisne, and the
British guns were outranged and outnumbered. The spotting of hostile
batteries became an operation of the first importance, and the Flying
Corps quickly rose to its opportunities. When trench warfare began, the
aeroplanes attached to corps commands took up artillery officers daily
from each division over the German batteries. The positions of these
batteries were noted on maps, and the maps were sent in every day to the
divisional artillery commander, who allotted the targets to his
batteries. When any part of the British lines was shelled, information
was obtained from the air and orders were given to those of our
batteries which could best reply, to concentrate on the enemy's guns.
The wireless machines of No. 4 Squadron had been attached to the army
corps direct during the battle of the Marne, but their opportunities had
been few. On the Aisne they were first used to observe for the
artillery. Two pioneers of wireless telegraphy are associated in work
and in memory with these early attempts at wireless co-operati