The main cavern in which the girls had waited for the storm to blow over was of considerable size, as they had thought at that time; and the domed roof was very high. The hill really was a great hollow.
There were passages into several smaller caves; but these were mere pockets beside the larger apartment. Wherever there was any appearance of the floor of the cavern having been disturbed, the men used the spade and bar. But they found no hidden treasure. In fact, the floor was mostly of solid rock. The old bandit would have found it difficult to have buried anything under such flooring.
It seemed as though they had searched the place thoroughly, and all the little chambers, too, when Walter's torch revealed to him a crack in the wall at the far end of the cavity, and almost as high as his head. He soon called the others to come and examine this place.
"A big boulder has been rolled into an opening. That is what it is," said Nan.
"Just what I was saying to myself," Walter confessed. "And I believe nature did not roll the rock here, either."
"Think somebody shut the door on a passage, do you?" asked Tom
Collins, curiously. "Bring along the bar, Hess, and let's see."
"If nature did not wedge that rock into the opening, then whoever did it did an excellent job!" growled Walter, after working on the boulder for a couple of hours.
"It's started. Yes, it's started," said Tom complainingly. "But you can't say much more about it and speak the truth. If that old Mexican's treasure ain't behind that rock, then it ought to be, that's sure!"
Supper time came, and they were still working at the boulder. It was agreed to camp in the cavern for the night, and continue working at the wedged rock until bedtime.
"And might as well bring the ponies in and hobble 'em, eh?" suggested Tom Collins. "No use standing watch on 'em outside. They've grazed themselves full this afternoon."