The boys raced like mad for camp.
With every light available from both machines set in one of the biplanes, fore and aft, the young aviators sailed through the shadows, got their bearings from the big rock and fearlessly swooped into the lower strata.
The glittering gondola of the air trailed a line of illumination along the rugged face of the chasm wall, but in the first passing, Henri, as observed, gave no signal of discovery.
The insistent hum of the motors prevented the hearing of any hail that might be given from without, and as effectually drowned any call from within the machine.
"Another round, Billy boy," shouted Henri, "a little lower down."
The next circle and come-back brought results, attested by a gleeful hurrah from the observer.
"There's a man on the ledge over there—there's two, by jingo! Round again, pard. Steady now!"
The aëroplane was dangerously near the ledge, a little above it. Henri was standing, one hand gripping a stay for balance, and in the other grasping a ball of whipcord. With a sharp turn the pilot nosed away, the tail lights of the machine gleamed full for an instant upon the dark figures silhouetted on the rock face, and in that precious, fleeting instant, with a round arm swing, Henri sent the cord ball, unwinding as it dropped, straight down upon the ledge.
"Up!" sang out the maker of the successful throw, and as the biplane made almost perpendicular ascent, it tugged, kite like, at a long line of cord, paid out by one of the men left behind on the rocky shelf.
Once out of the canyon, the pilot checked his flight at the first level, and both boys, under the glare of the searchlight, speedily spliced and knotted two coils of fine-fibered rope, part of the flying equipment.