"But I mean the pumas or jaguars that seem to have here and there turned the cells into caves, and left their gnawed bones about. They may have lived here fifty years ago, a hundred years, or five. But there is one thing evident, and it is this--that the people who lived here chose the place as being one that they could make into a stronghold, one which they could fortify so as to defend themselves from their enemies."

"What enemies, sir?" asked Ned sharply.

"Ah, that I can't tell you. The people here must have been to a great extent civilised, or they would not have been builders; and most likely their enemies were wild Indian-like tribes who roamed the plains, as they do to this day. I want to find something left by these builders, and then perhaps we might learn something."

They had now come to the last of the long range of cells that they had been making their way through, and further progress was checked by solid rock which had evidently been neither chipped away nor added to.

They cautiously stepped through the front opening, to stand upon the rough, crumbled-away terrace, from which they could look down into the great depression where the ponies and mules were contentedly grazing, and for about the tenth time looked upward for some means of reaching the terrace above, one which appeared more time-worn and dangerous than that upon which they stood; but without ladders it would have been risking life to make any attempt to reach it.

"Strikes me, sir," said Griggs, "that we've left the way up far behind."

"Why?" said Wilton sharply.

"Because we've seen no way here, and we found one there."

"But _I_ could see nothing likely to lead higher," said Chris.

"We didn't look about much," cried Ned. "We were eager to come along here."

"Yes, I suppose that was so," said Chris thoughtfully. "Well, there's the row of cells above us, and there must be a way."

"Unless it has been swept off by some landslip," suggested Bourne.

"Well, we'll turn back now," said the doctor, "for even if we had a shovel I don't think we should find anything that would help us."

They went back from cell to cell, and twice over found the terrace outside sufficiently level and secure to allow of their pa.s.sing along it, but they soon had to take to the interior again with its low doorway-like connections.

At last they all stood together at the top of the roughly-stepped sloping shaft by which they had ascended, to find that the roof here was entirely broken away by the falling of a portion of the cliff; but they found also what they sought, for there, about a score of feet above their heads, was the evident continuation of the shaft-like hole by which they had come up.

"Look," cried Griggs triumphantly; "no wonder we could not find it."

"But how are we to use it?" said Bourne.

"Oh, we can manage that, sir; eh, boys?"

"You might," said the doctor, gazing up, "but I'm sure I couldn't."

"Oh yes, you could, sir, when one of us has been up and driven a peg here and a peg there into some of those cracks. The stones are quite in layers; and after that we'll drive a very strong one in, and tie a lariat to it to hang down like a bal.u.s.trade to steady whoever goes up."

"But where are the pegs?"

"Down below, sir, growing in amongst those trees. I vote we go down, have some dinner, and come up again after I have chopped as many pegs as I think we shall want. I should bring the axe up here too, so as to drive them in. Why, Chris, lad, we could make a regular ladder up there."

Griggs' proposal was adopted, and that same afternoon found them in the same place, with the American ready for action, and the boys carrying rope and pegs.

And now what had seemed difficult before had grown easy, the American, who had cut plenty of tough short pieces of pine and formed them chisel-ended, driving one in between the natural faults in the stone with the head of the axe, and then climbing upon it to drive in another, which formed a standing-place in turn, the slope upward of the cliff making the task easy--so easy, in fact, that less than half-an-hour sufficed to bring him to the spot where the shaft was in fair preservation, with its projecting pieces of stone left by the original carvers of the way.

Here the American fixed the strong peg pitched up to him by Chris, who had followed him up step by step, and after tying to it one end of the lariat thrown up by Ned, the two workers made their way up to the intact shaft, and reached the first cell of the next row, some fifty feet above the other, gaining at the same time a better view of the terrace in front, and seeing that it was comparatively very little broken-down, merely worn by the weather.

"Here, let's go on a little way," cried Chris eagerly.

"No," replied Griggs; "fair play's a jewel. Let's go back; your father will like to be one of the first to begin exploring."

"So he will; but look, here they come."

For Ned was close up, being the next to test the stability of the new ladder, and was closely followed by the doctor and their other friends.

"Capital!" cried the doctor. "A much finer view from up here. Why, with such a stronghold and no better way for the enemy to approach, the old people ought to have been able to set all the tribes of the plain at defiance."

"Perhaps they did, sir," said Griggs; "but it seems to me that they must have had a regular channel of water coming down from above there to supply all these rooms, or cells, as you call them."

"Most likely," said the doctor.

"How would it be then if the enemy managed to break down the channel from somewhere up yonder where we found the hole under the fallen stones? Could the people who attacked them have done that?"

"Why, Griggs, you are making history. That was the old people's aqueduct, and it is quite possible that when they were besieged the enemy caused the destruction over which we climbed."

"Yes," said Griggs thoughtfully; "that would ruin the folk. No doubt some of these places were used as stores, and those might last for years; but if their supply of water were cut off there wouldn't be much chance for them then."

"Well, let's see farther," said the doctor. "I can't help thinking that they must have been a strong and fairly civilised race."

Chris led the way in, to find the cell he entered cut out and built-up just the same as those which they had seen; but the floor was enc.u.mbered deeply with the dust of ages, and on stirring some of it with his foot the boy drew back hurriedly and looked strangely at his father.

"What have you found?" said the doctor.

"The jaguars must have killed a man here, father," replied the boy, who looked on in disgust as his father stepped in and picked up a skull which might have lain there, sheltered by the roofing of stone, for ages. It looked brown and as if very little pressure would suffice to crumble it up into dust; but the teeth left in the upper jaw were perfect and fairly white.

"Ah!" said the doctor thoughtfully. "Here's a bit of genuine history at last."

"Killed by a jaguar, father?" cried Chris excitedly.

"No, my boy," was the reply; "this is not the marking of a jaguar's teeth, but the cause of death, plainly enough."

"What, that hole?" cried Chris excitedly.

"Yes. Look, the forehead has been crushed in by the blow from a stone axe, or possibly by a stone hurled from above."

"Perhaps only held in the hand, sir," said Griggs thoughtfully.

"Why, that's a heap of old bones," cried Ned, with a look of horror; "the dust's full of them."

"Yes," said the doctor, moving the relics carefully with the b.u.t.t of his rifle for fragments that were fully defined as to shape to fall together as mere dust and hide portions below. "There's another skull,"

continued the examiner, "crushed in more than the first. A finely-preserved specimen, for, in spite of that hole, it shows the shape of the relic--a low forehead, retreating very rapidly, the brows very bony and heavy, and the cheek-bones widely prominent."

"That's not the same shaped skull as the first," said Bourne quickly.

"Certainly not," replied the doctor. "I should say it belonged to a fiercer, more savage race of man, who might have been an ancestor of the present Indians of the plains."