could advance, although these ranged all the way from cannibals and gorillas to ghosts, had any effect on the solution of the mystery. The

e. 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. L

sharply after the sending had be

ue feeling of apprehension. He speedily drove

ss night I passed h

and the boys started, as soon as the camp had been put in order, on their expedition up the mountain-s

quipment, it was rendered even tougher. All three carried water-canteens covered with wet felt, containing half-a-

es over which the adventurers were making their way, it became as unc

xclaimed Harry, "I feel like a piece of bu

ebit myself," laughed Fr

me," growled the veteran angrily; "consarn these rocks, I'd

ide, frequently using the rope-ladder to get over rough places, and at about noon

a straight line from the point down the southern slope of the mountain-side. While they were busy about this they were star

-H-O-O-O-a-h-o

Harry, "what on earth

ade a determined effort to ascertain the source of

shouted; now wit

s brother had suddenly become infected with

w where it comes from,"

horused Be

Upturned Face," cried Fr

rang out once more. Th

from the sinister countenance car

for all time," shouted Frank, drawing

y dashed back up the mountain-side utterly oblivious now to the heat or anything but their determination to discover who or what had u

d I'll travel right along the face till

a height where he could lay hold of a projecting bit

are a fly and try to brush you

d back Frank, "unless I lit

face was as remarka

of the rocks and had cut into the flat surface, which was upturned to the sky, eyes and a mo

ere came a repetition of the weird cry, but this time the lad w

m his very feet. Then, all at

roceeded from the mo

of the steep declivity

face below there very carefully for any holes.

ounced the searchers

ther," ord

ny Harry shouted that they had found a row of small h

the mystery of the vo

u mean?" de

ch, when the wind blows in a stiff puff, air is forced with violence enou

rica, carved out by some forgotten race, and the weird cries that the vent-holes give o

s they all buckled over the simple explanation of the phenomenon that had caused the

ever heard," said Frank, "and now having sol

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 before they laid out a fresh hundred feet. In this way they must h

ds they had reached the pile, which they knew meant the discovery of the ivory cache and the end of the most difficult part of their

s!" exclaimed Frank, as they

reason for the

se of the pile were a doz

n?" asked Harry in an awed

killed them after they erected the cache so that they would not be able to spread the knowledge of its whereabouts

up and saw the old adventurer pointing to the mountain summit where it cut the sky. Outlined against the deep azure was

strange, crouched fo