used by the diversion of the course of
bullets, which struck the revolving propellers, it actually saved
for effective use about thirty per cent. of the ammunition employed.
As the amount of ammunition which can be carried by an airplane is
rigidly limited this gave to the appliance a positive value.

[Illustration: _The Terror that Flieth by Night._

_Painting by William J. Wilson._]

Reference has been made to the extraordinary immunity of flying
airplanes to the attacks of anti-aircraft guns. The number of wounds
they could sustain without being brought to earth was amazing.
Grahame-White tells of a comparison made in one of the airdromes of
the wounds sustained by the machines after a day's hard scouting and
fighting. One was found to have been hit no less than thirty-seven
times. Curiously enough the man who navigated it escaped unscathed.
Wounds in the wings are harmless. But the puncture of the fuel tank
almost certainly means an explosion and the death of the aviator in
the flame thousands of feet in the air. During an air battle before
Arras, a British aviator encountered this fate. When his tank was
struck and the fusillage, or body, of his machine burst into flames,
he knew that he was lost. By no possibility could he reach the
ground before he should be burned to death. A neighbouring aviator
flying not far from him told the story afterwards:

Jack was not in the thick of this fight [said he]. He was rather
on the outskirts striving to get in when I suddenly saw his whole
machine enveloped in a sheet of flame. Instantly he turned
towards the nearest German and made at him with the obvious
intention of running him down and carrying him to earth in the
same cloud of fire. The man thus threatened, twisted and turned
in a vain effort to escape the red terror bearing down upon him.
But suffering acutely as he must have been, Jack followed his
every move until the two machines crashed, and whirling over and
over each other like two birds in an aerial combat fell to earth
and to destruction. They landed inside the German lines so we
heard no more about them. But we could see the smoke from the
burning debris for some time.

As the range of anti-aircraft guns increased the flyers were driven
higher and higher into the air to escape their missiles. At one time
4500 feet was looked upon as a reasonably safe height, but when the
war had been under w