[Illustration: _The Terror that Flieth by Night._
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 aërial 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 débris 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 way about two years the weapons designed to combat aircraft were so improved that they could send their shots effectively 10,000 feet into the air. If the aircraft had been forced to operate at that height their usefulness would have been largely destroyed, for it is obvious that for observation purposes the atmospheric haze at such a height would obscure the view and make accurate mapping of the enemy's position impossible. For offensive purposes too the airplanes at so great an elevation would be heavily handicapped, if not indeed rendered impotent. As we shall see later, dropping a bomb from a swiftly moving airplane upon a target is no easy task. It never falls direct but partakes of the motion of the plane. It is estimated that for every thousand feet of elevation a bomb will advance four hundred feet in the direction that the aircraft is moving, provided its speed is not in excess of sixty miles an hour. As a result marksmanship at a height of more than five thousand feet is practically impossible.