Some other pilot had doubtless been over this same route on previous occasions; yes, and even landed in that identical field. He had made the chart; and the accompanying memoranda consisted of his personal experiences.
Already the moon had dispelled some of the cheerless gloom round about them. It was still cold up in that upper strata of rarefied air; but their fur-lined garments kept them from suffering. Besides this, they were young and vigorous, and their blood was warm, and they were excited with their mission and able to ignore any physical discomfort that might come to them.
Jack continued to stare ahead as time passed. He was looking for some sign of the city towards which they were flying. Tom, on his part, often took note of his compass, then flashed a glance up at the stars, and finally sought to discover some landmark far down below that was marked upon the chart.
He had the utmost confidence in his own judgment, and believed he would bring up at the identical place which was their goal.
Tom now volplaned again, wishing to draw nearer to the earth. It was while thus dropping, with engine muffled, that his ears caught a sound calculated to give him an uneasy feeling.
This was undoubtedly the whirr of a propeller beating the air in furious fashion. It also came from behind. Jack, too, had caught the sound, and was thrilled with sudden apprehension of impending trouble.
They were undoubtedly being pursued, and by a much faster plane than their own. This would mean that presently they would be overtaken and fired upon. It was not in the nature of Tom Raymond to allow such a thing to occur and be kept from doing his share of the fighting.
When Tom swung around to face the rear, and actually started to run toward the oncoming foe, Jack knew what was expected of him. He must man the gun, and prove how well he had learned his lesson when at school at Pau and at Casso.
No longer could they expect to be guided by sounds. Their own motor thundered so loudly that every other sound was deadened. They must depend on eyesight alone to tell them when they were nearing the oncoming Fokker craft. Perhaps the first indication they would have of its presence would be the flash of its quick-firing gun, spattering bullets around them like hail.
So Jack strained his vision to the limit. He was eager to discover the enemy before they themselves were seen. Much might depend on who fired first, in a duel of this kind.