Presently they came to a shallow depression resembling a North American gulch or a South African drift, only bone-dry. At one time it had been a watercourse. The bed was littered with small stones.
Uncle Brian stooped, picked up one of the rough pebbles, and examined it.
"Would you like to be rich beyond the dreams of avarice, Peter?" he asked. "If so, load up. These are rough diamonds."
His nephew looked incredulous. He half suspected that the sun, following the concussion of the crash, had affected his uncle's brain.
"Fact," continued Brian Strong. "The quantity of diamonds here would make the De Beer's reserve look silly in comparison. We'll take a few—just a few—to support our statement, should we be lucky enough to come through. Personally, I'd rather have a pint of pure water at the present time.... Enough, Peter! Don't sacrifice mobility to cupidity. Later on, perhaps."
In his present state of mind, Peter, once he was convinced of the sincerity of his uncle's announcement, was not greatly impressed by the magnitude of the discovery. The mere fact that untold wealth lay at his feet was as nothing compared with his anxiety to get clear of the mountain-enclosed arena. He hardly doubted his ability to find a way out; but it was the long and tedious tramp that rather appalled him. The change from speedy flying to a trudge afoot at two and a half miles an hour, when time was of the utmost importance, was a disconcerting prospect.
"There's an outlet," declared Uncle Brian, pointing to a bluff that even at a short distance merged into the sombre greyness of the mountainous wall. "We'll find a gorge close to it."
"Let's hope so," added Peter.
"There must be some egress," continued Uncle Brian. "At some time—centuries ago—when this place was a lake—the overflow escaped in a northerly direction. Why? Because to the south'ard are the Sierras, which form a watershed between Rioguay and Venezuelan territory. For some reason—an earthquake, most likely—the feeders dried up or were diverted. Consequently, the lake ran dry. Yes, here we are."
The cleft was so narrow that there was barely room for the two men to walk abreast. The walls, up to a height of thirty feet, were quite smooth, bearing evidence of the friction of sand and water for countless ages. Above that height they were rugged and irregular, so that in many places the sky was completely shut out from view.