Presently they were going forward. It was new ground to the professor, as well as to the others, for he had never been in the tunnel. This latter was evidently a hollow shaft under the mountain, caused by an earthquake perhaps, or, more probably, by the erosion of an underground river.
The tunnel was about ten feet high and about as broad, being oval in shape. There was room to drive many cattle along it, and there were evidences that many had been so driven.
“Go a bit easy,” advised Ned. “We don’t want to burst out of the other end of this shaft into the midst of the rustlers.”
“Oh, the tunnel is about a mile long,” said the professor. “And the end is screened by bushes, so you’ll have plenty of chance to be on your guard.”
They hurried silently along the big rocky shaft, their electric flashlight casting queer, flickering shadows on the walls. The professor took the lead when they judged they had covered nearly the distance estimated, and presently he came to a halt.
“We’re near the end,” he said, indicating a glimmer of daylight. “Better put out your electrics.”
This the boys did. Then, proceeding still more cautiously, they presently found themselves looking through a screen of bushes at a curious sight.
Down in a sort of gigantic bowl of a valley, the presence of which they had not detected in their wanderings, as it was the depressed top of a big, deeply wooded hill, they saw a score or more of cowboys and a herd of steers, the latter being driven hither and yon in the process of having the brand of the Square Z ranch obliterated, and another substituted.
“The rustlers!” whispered Jerry.