But, happily, there were limits to the strain which the rope would stand, though none apparently to the lifting powers of this infernal machine.
There was a sharp crack, and we were in a heap upon the ground with coils of rope all over us.
When we were able to stagger to our feet we saw far off in the deep blue sky one dark spot where the lump of basalt was speeding upon its way.
"Splendid!" cried the undaunted Challenger, rubbing his injured arm.
"A most thorough and satisfactory demonstration!
I could not have anticipated such a success.
Within a week, gentlemen, I promise that a second balloon will be prepared, and that you can count upon taking in safety and comfort the first stage of our homeward journey."
So far I have written each of the foregoing events as it occurred. Now I am rounding off my narrative from the old camp, where Zambo has waited so long, with all our difficulties and dangers left like a dream behind us upon the summit of those vast ruddy crags which tower above our heads.
We have descended in safety, though in a most unexpected fashion, and all is well with us.
In six weeks or two months we shall be in London, and it is possible that this letter may not reach you much earlier than we do ourselves.
Already our hearts yearn and our spirits fly towards the great mother city which holds so much that is dear to us.
It was on the very evening of our perilous adventure with Challenger's home-made balloon that the change came in our fortunes.
I have said that the one person from whom we had had some sign of sympathy in our attempts to get away was the young chief whom we had rescued.
He alone had no desire to hold us against our will in a strange land. He had told us as much by his expressive language of signs.
That evening, after dusk, he came down to our little camp, handed me (for some reason he had always shown his attentions to me, perhaps because I was the one who was nearest his age) a small roll of the bark of a tree, and then pointing solemnly up at the row of caves above him, he had put his finger to his lips as a sign of secrecy and had stolen back again to his people.
I took the slip of bark to the firelight and we examined it together.
It was about a foot square, and on the inner side there was a singular arrangement of lines, which I here reproduce: They were neatly done in charcoal upon the white surface, and looked to me at first sight like some sort of rough musical score.
"Whatever it is, I can swear that it is of importance to us," said I.
"I could read that on his face as he gave it."
"Unless we have come upon a primitive practical joker," Summerlee suggested, "which I should think would be one of the most elementary developments of man."
"It is clearly some sort of script," said Challenger.
"Looks like a guinea puzzle competition," remarked Lord John, craning his neck to have a look at it. Then suddenly he stretched out his hand and seized the puzzle.
"By George!" he cried, "I believe I've got it.
The boy guessed right the very first time.
How many marks are on that paper?
Well, if you come to think of it there are eighteen cave openings on the hill-side above us."
"He pointed up to the caves when he gave it to me," said I.
"Well, that settles it.
This is a chart of the caves.
What! Eighteen of them all in a row, some short, some deep, some branching, same as we saw them.
It's a map, and here's a cross on it.
What's the cross for?
It is placed to mark one that is much deeper than the others."
"One that goes through," I cried.
"I believe our young friend has read the riddle," said Challenger.
"If the cave does not go through I do not understand why this person, who has every reason to mean us well, should have drawn our attention to it.
But if it does go through and comes out at the corresponding point on the other side, we should not have more than a hundred feet to descend."
"A hundred feet!" grumbled Summerlee.
"Well, our rope is still more than a hundred feet long," I cried.
"Surely we could get down."
"How about the Indians in the cave?" Summerlee objected.
"There are no Indians in any of the caves above our heads," said I.
"They are all used as barns and store-houses.
Why should we not go up now at once and spy out the land?"
There is a dry bituminous wood upon the plateau—a species of araucaria, according to our botanist—which is always used by the Indians for torches.
Each of us picked up a faggot of this, and we made our way up weed-covered steps to the particular cave which was marked in the drawing.
It was, as I had said, empty, save for a great number of enormous bats, which flapped round our heads as we advanced into it.
As we had no desire to draw the attention of the Indians to our proceedings, we stumbled along in the dark until we had gone round several curves and penetrated a considerable distance into the cavern. Then, at last, we lit our torches.