CHAPTER X
THE ARAB'S CACHE
The mysterious cries were not repeated that night although the boyslaid awake till daylight listening for any repetition. No theorythey could advance, although these ranged all the way from cannibalsand gorillas to ghosts, had any effect on the solution of themystery. They finally agreed to trust to solving it in some chanceway, and like sensible boys did not continue to worry themselvesover the unsolvable.
Frank's first action was to send out a wireless to the river campand to his great relief he found that events there were stillproceeding with the same regularity as before. Nothing had occurredto mar the even life of the young adventurers left behind. This wasthe tenor of the message, but there was something about it thatworried Frank. Lathrop, he knew, was an expert wireless operator,but the sending that he performed that morning was so jerky andirregular that the rankest amateur might have done better.
"What is the matter?" asked Frank sharply after the sending hadbecome even more unskilled and shaky.
There was no answer; which caused Frank a vague feeling ofapprehension. 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 moretime to waste on gloomy forebodings and the boys started, as soon asthe camp had been put in order, on their expedition up themountain-side to the Upturned Face--which was to be the startingpoint for the uncovering of the secret ivory hoard.
The climb was quite as stiff as Frank had anticipated and, laden asthey were with the rope-ladder and the other equipment, it wasrendered even tougher. All three carried water-canteens coveredwith wet felt, containing half-a-gallon each. Frank had insisted onthis as it was doubtful if they could find water at the summit ofthe mountain.
As the sun rose higher in the sky and beat down on the bare rockridges over which the adventurers were making their way, it becameas uncomfortable as any expedition on which the boys had ever beerengaged.
"Talk about New Mexico or Death Valley," exclaimed Harry, "I feellike a piece of butter rolled up in a paper and I've melted."
"I feel like a Welsh rarebit myself," laughed Frank, "how about you,Ben?"
"I feel like a pot of boiling tar with a fire lighted under me,"growled the veteran angrily; "consarn these rocks, I'd give a wholelot for a bit of that shade we left behind us."
Despite the discomfort and the heat, however, they struggled on upthe mountain-side, frequently using the rope-ladder to get overrough places, and at about noon they stood beneath the steep rockcliff that formed the nose of the upturned face.
It was easy enough then to reach a spot below the tip and Frank,with a long cord he had brought for the purpose, laid out a straightline from the point down the southern slope of the mountain-side.While they were busy about this they were startled by a repetitionof the same strange cry, half-warning, half-savage, that they hadbeen so alarmed by the night before.
"A-ho-o-o-o-AH-H-O-O-O-a-h-o-o-hoo-o-o-o-o!"
"Great Scott," yelled Harry, "what on earth do you think of that?"
Frank--considerably startled himself--had, however, made adetermined effort to ascertain the source of the sound as it roseand fell in its strange cadence.
"I've got it!" he shouted; now with a cry of triumph.
"Got what?" cried Harry, as if he feared his brother had suddenlybecome infected with some strange complaint--"rabies or the pip?"
"The noise--I mean I know where it comes from," cried the excitedboy.
"Where?" chorused Ben and Harry.
"From somewhere about the Upturned Face," cried Frank triumphantly,"Hark!"
The strange wailing cry rang out once more. They all listenedintently.
Sure enough it seemed to proceed from the sinister countenancecarved in the living rock above them.
"Well, here's where we end this mystery for all time," shoutedFrank, drawing his revolver, "who is game to follow me?"
Of course Harry and Ben rushed to his side, and while the echo ofthe mysterious cry was still sobbing and sighing among the cragsthey dashed back up the mountain-side utterly oblivious now to theheat or anything but their determination to discover who or what haduttered the extraordinary cry. The side of the nose--or the nostrilso to speak--was formed of a wall of rock fully twelve feet inheight.
"You fellows give me a boost up there and I'll travel right alongthe face till I find out where the racket comes from."
On Ben's strong shoulders Frank was soon hoisted up to a heightwhere he could lay hold of a projecting bit of rock and shin himselfup on to the top of the nose.
"Look out he doesn't think you are a fly and try to brush you off,"laughed Harry from below.
"No danger of that," shouted back Frank, "unless I lit on him in theGolden Eagle."
The surface of the face was as remarkable as its profile.
Apparently some forgotten tribe had at some time or other beenstruck by the facial outline of the rocks and had cut into the flatsurface, which was upturned to the sky, eyes and a mouth, the latterwell provided with teeth, in each of which was drilled a tinytriangular hole.
While Frank was puzzling over the meaning of these apertures therecame a repetition of the weird cry, but this time the lad was sostartled that he almost lost his balance and fell backward.
The call seemed to proceed from his very feet. Then, all at once,he realized what it was.
The strange sounds proceeded from the mouth of the stone face.
Frank ran to the edge of the steep declivity that formed the nose.
"Say, Harry, and you too, Ben, examine the surface below there verycarefully for any holes. They will probably be small ones and in arow."
"None this side," announced the searchers after a lengthy quest.
"Try the other," ordered Frank.
They did so and after a few minutes of careful scrutiny Harryshouted that they had found a row of small holes pierced in the rockjust below where Frank stood.
"Then we have solved the mystery of the voice," exclaimed Frank.
"What do you mean?" demanded Harry.
"That it is nothing more or less than an arrangement of holesthrough which, when the wind blows in a stiff puff, air is forcedwith violence enough to cause the cry that disturbed us so much lastnight," was the reply.
This indeed was the solution, and had the boys known it there aremany such rocks in Africa, carved out by some forgotten race, andthe weird cries that the vent-holes give out in the wind doubtlessacted as a powerful "fetish" to keep away troublesome enemies.
"No wonder the niggers down below don't come near the MoonMountains," said Harry, as they all buckled over the simpleexplanation of the phenomenon that had caused them so much alarm."I wouldn't care to, myself, unless I knew just what made that cry."
"It certainly was as depressing as anything I ever heard," saidFrank, "and now having solved the great mystery--let's get back towork."
The three adventurers went at the job with a will. The line wasabout a hundred feet long and the method of procedure was this:Frank tested the straightness of the line, as accurately as possiblewith his eye, while Ben and Harry carried it stretched between them.The end of each hundred feet was signalized by a stone, and Harry,who was at the end of the line, carried his end to this mark beforethey laid out a fresh hundred feet. In this way they must havemeasured off very nearly half-a-mile of the mountain-side when Frankgave a sudden sharp cry and pointed to a depression in the darkrange immediately below them. As the others looked they echoed hiscry and gave a dash forward.
Directly beneath them, about in the center of the little dip, was acairn of rough stones perhaps four feet in height. In a few boundsthey had reached the pile, which they knew meant the discovery ofthe ivory cache and the end of the most difficult part of theirexpedition. Little did they imagine the amazing things that wereyet to happen to them and of which they were but on the threshold.
&
nbsp; "Good Lord, look at that, boys!" exclaimed Frank, as they stood atthe foot of the cairn.
There was a good reason for the boy's exclamation.
Distributed around the base of the pile were a dozen or, more humanskulls.
"Are they those of white men?" asked Harry in an awed tone. Frankshook his head.
"No, they are those of negroes I believe," he replied after acareful examination, "and I imagine that Muley-Hassan killed themafter they erected the cache so that they would not be able tospread the knowledge of its whereabouts to any of the maraudingtribes who might even brave the ghostly voice when such a greattreasure of ivory tempted."
A shout from Ben, who had been walking round the pile examining itfrom every view-point interrupted them. They looked up and saw theold adventurer pointing to the mountain summit where it cut the sky.Outlined against the deep azure was the object that had caused hisexclamation. It was the figure of a man that had apparently beenwatching them intently.
But as they gazed the strange, crouched form suddenly vanished.