CHAPTER X
THE ARAB'S CACHE
The mysterious cries were not repeated that night although the boys laid awake till daylight listening for any repetition. No theory they could advance, although these ranged all the way from cannibals and gorillas to ghosts, had any effect on the solution of the mystery. They finally agreed to trust to solving it in some chance way, and like sensible boys did not continue to worry themselves over the unsolvable.
Frank's first action was to send out a wireless to the river camp and to his great relief he found that events there were still proceeding with the same regularity as before. Nothing had occurred to mar the even life of the young adventurers left behind. This was the tenor of the message, but there was something about it that worried Frank. Lathrop, he knew, was an expert wireless operator, but the sending that he performed that morning was so jerky and irregular that the rankest amateur might have done better.
"What is the matter?" asked Frank sharply after the sending had become even more unskilled and shaky.
There was no answer; which caused Frank a vague feeling of apprehension. He speedily drove this impression from his mind, however, with:
"Pshaw! the sleepless night I passed has made me nervous."
After breakfast there was so much to be done that there was no more time to waste on gloomy forebodings and the boys started, as soon as the camp had been put in order, on their expedition up the mountain-side to the Upturned Face—which was to be the starting point for the uncovering of the secret ivory hoard.
The climb was quite as stiff as Frank had anticipated and, laden as they were with the rope-ladder and the other equipment, it was rendered even tougher. All three carried water-canteens covered with wet felt, containing half-a-gallon each. Frank had insisted on this as it was doubtful if they could find water at the summit of the mountain.