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
