The beetling head of the cliff projected over the cane-brake.
Undoubtedly he had fallen from above.
But had he fallen?
Had it been an accident?
Or—already ominous and terrible possibilities began to form round that unknown land.
We moved off in silence, and continued to coast round the line of cliffs, which were as even and unbroken as some of those monstrous Antarctic ice-fields which I have seen depicted as stretching from horizon to horizon and towering high above the mast-heads of the exploring vessel.
In five miles we saw no rift or break.
And then suddenly we perceived something which filled us with new hope.
In a hollow of the rock, protected from rain, there was drawn a rough arrow in chalk, pointing still to the westwards.
"Maple White again," said Professor Challenger.
"He had some presentiment that worthy footsteps would follow close behind him."
"He had chalk, then?"
"A box of colored chalks was among the effects I found in his knapsack.
I remember that the white one was worn to a stump."
"That is certainly good evidence," said Summerlee.
"We can only accept his guidance and follow on to the westward."
We had proceeded some five more miles when again we saw a white arrow upon the rocks.
It was at a point where the face of the cliff was for the first time split into a narrow cleft.
Inside the cleft was a second guidance mark, which pointed right up it with the tip somewhat elevated, as if the spot indicated were above the level of the ground.
It was a solemn place, for the walls were so gigantic and the slit of blue sky so narrow and so obscured by a double fringe of verdure, that only a dim and shadowy light penetrated to the bottom.
We had had no food for many hours, and were very weary with the stony and irregular journey, but our nerves were too strung to allow us to halt.
We ordered the camp to be pitched, however, and, leaving the Indians to arrange it, we four, with the two half-breeds, proceeded up the narrow gorge.
It was not more than forty feet across at the mouth, but it rapidly closed until it ended in an acute angle, too straight and smooth for an ascent.
Certainly it was not this which our pioneer had attempted to indicate.
We made our way back—the whole gorge was not more than a quarter of a mile deep—and then suddenly the quick eyes of Lord John fell upon what we were seeking.
High up above our heads, amid the dark shadows, there was one circle of deeper gloom.
Surely it could only be the opening of a cave.
The base of the cliff was heaped with loose stones at the spot, and it was not difficult to clamber up.
When we reached it, all doubt was removed.
Not only was it an opening into the rock, but on the side of it there was marked once again the sign of the arrow.
Here was the point, and this the means by which Maple White and his ill-fated comrade had made their ascent.
We were too excited to return to the camp, but must make our first exploration at once.
Lord John had an electric torch in his knapsack, and this had to serve us as light. He advanced, throwing his little clear circlet of yellow radiance before him, while in single file we followed at his heels.
The cave had evidently been water-worn, the sides being smooth and the floor covered with rounded stones.
It was of such a size that a single man could just fit through by stooping.
For fifty yards it ran almost straight into the rock, and then it ascended at an angle of forty-five.
Presently this incline became even steeper, and we found ourselves climbing upon hands and knees among loose rubble which slid from beneath us.
Suddenly an exclamation broke from Lord Roxton.
"It's blocked!" said he.
Clustering behind him we saw in the yellow field of light a wall of broken basalt which extended to the ceiling.
"The roof has fallen in!"
In vain we dragged out some of the pieces. The only effect was that the larger ones became detached and threatened to roll down the gradient and crush us.
It was evident that the obstacle was far beyond any efforts which we could make to remove it.
The road by which Maple White had ascended was no longer available.
Too much cast down to speak, we stumbled down the dark tunnel and made our way back to the camp.
One incident occurred, however, before we left the gorge, which is of importance in view of what came afterwards.
We had gathered in a little group at the bottom of the chasm, some forty feet beneath the mouth of the cave, when a huge rock rolled suddenly downwards—and shot past us with tremendous force.
It was the narrowest escape for one or all of us.
We could not ourselves see whence the rock had come, but our half-breed servants, who were still at the opening of the cave, said that it had flown past them, and must therefore have fallen from the summit.
Looking upwards, we could see no sign of movement above us amidst the green jungle which topped the cliff.