That night they carefully studied their map, on which the location of the Hidden Valley had been marked as accurately as possible, as they had done so many times before. And at daybreak on the following morning Ted loaded the packages into the ship, while Stanley went for a conference with the colonel. When the latter, too, arrived on the field, the plane was on the line with the engine roaring. Although the guards assured them that none had approached the hangar during the night, the two spent considerable time in a minute inspection of the machine. And when the sun was an hour high in the heavens they left the ground, circled the field until they had reached an altitude of several thousand feet, then headed straight to the north. If their calculations were right, they should reach the valley in an hour, unless they encountered a strong head-wind. Allowing another hour for the return, there would be a leeway of a third hour, for the fuel-supply, counting that contained in the emergency-tank overhead, was ample for three hours. From directly above, the mountain-peaks appeared flattened out exactly like the plateaux and valleys, but they could be distinguished from the latter by the patches of snow and fields of black rocks. A wind from the south added greatly to their speed, so that the landscape beneath them moved back at a rapid pace. To their right, and far, far below, lay the sea of dark-green Amazonian jungle. Here and there among the bleak mountain-peaks lay little green valleys with square, blocklike dots scattered about singly and in groups. To the casual observer they might have been mistaken for stones. But to the trained eye they were clearly Indian huts, distinguishable from the other objects by their regular outlines. And if Ted looked closely he could make out minute specks moving toward the houses; they were the Indians running to shelter, terrified, no doubt, by the roaring spectre in the sky. “Keep your eyes open wide,” Stanley shouted back to his companion after he had throttled down the motor so that its roar did not drown the sound of his voice. “Look for the yellow vapor and the ring of volcanoes. The wall, too. What was that?” A black form had passed them at great speed, its shadow blanketing one side of the craft. Ted looked back, knowing that it could not have been a cloud, for the sky was clear. “It’s a condor,” he called at the top of his voice, just as Stanley opened the throttle. Even as he spoke the great bird was wheeling gracefully and heading in their direction. Master of the desolate mountain tops and of the air above them, the huge bird was evidently investigating or challenging this newcomer into its realm.