“No doubt,” said the doctor, “and that accounts for so many of the stones of that breastwork being missing.”

“That’s right, sir. Well, I want to go down into that hole with a big light, and see what’s at the bottom there. I’m reckoning that we could find out what kind of weapons the enemy had to fight against the stones.”

“Yes,” cried Ned; “their swords and—”

“Well, I don’t know about swords, squire,” said the American dryly, “but they must have had something to fight with. I vote that we go and see.”

This was agreed to without hesitation on the doctor’s part, and the party made their way back to the top of the steps.

There was a pause here while all walked along the four sides, where hundreds of stones averaging the size of a man’s head lay just as they had been placed ages before; and then the descent was made to the opening at the side where the heap of dust had disappeared, and a short consultation took place.

“You’ll have to give up for to-day, Griggs,” said the doctor; “it’s as black as ink down there at the bottom.”

“That’s what I’ve been thinking, sir,” said Griggs. “One must have a lanthorn for this job, and by the time I’ve been to fetch it, got back here with another rope or two, and lit up ready for work, another hour will have slipped away; so if Chris and Ned here will promise not to tell me that I’m too much scared to go, I think I’ll give it up for to-night.”

“You may take it for granted that no one will even dream of such a thing,” said the doctor quietly; “and I think it will be much wiser to give up. We’ve done quite enough for one day. Every one for camp, a good wash, and a hearty meal.”

An hour later they were seated round their camp-fire, talking over the adventures of the day, and that night almost the same dream disturbed the slumbers of both boys, whose minds overleaped the long roll of ages which had elapsed, and conjured up for them the rock city occupied by a busy population. Then came the alarm of danger, the surprise made by the active enemy, and then the fierce defence of the first standing, the fight on the lower terrace, and the desperate defence of cell after cell. Then the fight for the next, and afterwards the escalading of the staircase in the great square hole, down into which Chris seemed to see scores of fierce-looking Indian warriors beaten by the stones cast from above.