Circling again and again it was with the utmost difficulty that they kept it in sight. At last, however, it struck a straight line for the cliffs.
"We can't get an aim if he keeps on swerving," said Herb.
"Steady, fellows," warned Hawke, for they had moved about, twisting in their seats, to get a sight of the game. The plane was mounting steadily higher, and Hawke had reduced his speed, pursuing the enemy as well as he could, for it had adopted a zigzag course, flying to right and left and dipping up and down.
"I'm going to try a shot anyway," said Herb.
The others unconsciously left the shooting to the southerner, who, it was naturally and rightly supposed, would be glad to bag the animal that had given his father so much trouble.
Young Phipps took aim at the first good opportunity, and shot three times. It seemed to be without result, for the huge shape moved on, though its course became more uncertain than ever, and, although it seemed heading toward the mountain ranges, its flight was uneven and hap-hazard.
"We must be over the mountains now," said Fly, after a time.
"We're about 1,800 feet above level," responded Hawke.
At that moment the bird resumed its swift circles, flying downward. Pointing the nose of the plane toward the earth, Hawke followed it, making a thrilling spiral descent.
"Why, there's the old tower," cried Fred, when the plane had dropped far enough for its lights to play upon the surface below.