The Boy Aviators in Africa Part 12

"A-hooo-A-AH-HOOO-00-a-ho-ho-ho-o-!"

It started softly and gradually ran up the scale till it reached a crescendo shout and then died out in a soft sound like a woman's wail. Heard anywhere the sound would have been alarming enough, but coming as it did in the midst of these unknown, mysterious Mountains of the Moon it struck a chill to the boy's heart and caused his scalp to tighten in a manner that even the bravest man or boy in the world would have had no reason to feel shame over.

A human enemy, a foe he could see, Frank would have faced with iron nerve; but this strange wailing noise coming from what quarter of the compa.s.s he could not judge--was so uncanny that he was really disturbed. He bounded into the cha.s.sis and roused Ben and Harry.

He had hardly whispered to them the extraordinary intelligence when again the voice arose.

"A-ho-ho-h-o-o-o-A-h-hoo-ho-AH-HO-HO-O-O-O-AH-ho-h-o-o-o-o-o-o!"

"Well, who?" roared Ben angrily, "come out and show yourself, you human hyena, and I'll put so much lead in your system you'll be worth a nickel a pound. Come, you old Ah-Hoo, and I'll show you who I am quick enough--shiver my topsails!"

But the only reply to Ben's tirade was the dismal echo of his voice among the rocky chasms.

"Shiver my topsails!" roared the echo and then the hills bandied the cry about from ridge to ridge till it died out in a whisper:

"My topsails!"

"Hum," remarked Ben, "I don't think I'll talk so loud around here.

There seem to be a lot of folks listening. Such a dreary hole as this I never--"

"Never," sighed the echoes, "--never."

"Here, I can't stand this," cried Harry. "I'm going to send a bullet up there the next time that fellow starts 'Ah-hooing."'

But as the strange mournful cry rang out once more the boys paused in bewilderment.

There was no locating the sound.

It seemed to fill the air. To come from every quarter of the compa.s.s at once.

CHAPTER X

THE ARAB'S CACHE

The mysterious cries were not repeated that night although the boys laid awake till daylight listening for any repet.i.tion. 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 pa.s.sed 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 h.o.a.rd.

The climb was quite as stiff as Frank had antic.i.p.ated 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.

As the sun rose higher in the sky and beat down on the bare rock ridges over which the adventurers were making their way, it became as uncomfortable as any expedition on which the boys had ever beer engaged.

"Talk about New Mexico or Death Valley," exclaimed Harry, "I feel like a piece of b.u.t.ter 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 whole lot for a bit of that shade we left behind us."

Despite the discomfort and the heat, however, they struggled on up the mountain-side, frequently using the rope-ladder to get over rough places, and at about noon they stood beneath the steep rock cliff 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 straight line from the point down the southern slope of the mountain-side.

While they were busy about this they were startled by a repet.i.tion of the same strange cry, half-warning, half-savage, that they had been 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 a determined effort to ascertain the source of the sound as it rose and 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 suddenly become infected with some strange complaint--"rabies or the pip?"

"The noise--I mean I know where it comes from," cried the excited boy.

"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 listened intently.

Sure enough it seemed to proceed from the sinister countenance carved in the living rock above them.

"Well, here's where we end this mystery for all time," shouted Frank, drawing his revolver, "who is game to follow me?"

Of course Harry and Ben rushed to his side, and while the echo of the mysterious cry was still sobbing and sighing among the crags they dashed back up the mountain-side utterly oblivious now to the heat or anything but their determination to discover who or what had uttered the extraordinary cry. The side of the nose--or the nostril so to speak--was formed of a wall of rock fully twelve feet in height.

"You fellows give me a boost up there and I'll travel right along the face till I find out where the racket comes from."

On Ben's strong shoulders Frank was soon hoisted up to a height where he could lay hold of a projecting bit of rock and shin himself up 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 the Golden Eagle."

The surface of the face was as remarkable as its profile.