Suddenly he straightened up with a flushed face. His countenance bore an angry look.
"Come here, fellows," he said, "and tell me what you make of this mark at the side of the rock."
He indicated a queer abrasion on one side of the stone. The living stone showed whitely where the lichen and moss had been scraped aside.
"Looks like some cuss had put a lever under it," pronounced Cal, after a careful inspection.
"That's what. Fellows, this rock was deliberately tilted so that it would come down on us and crush us. Now there's only one bunch of men that we know of mean enough to do such a thing and that's——"
Phut-t-t!
Something whistled past Nat's ear with a noise somewhat like the humming of a drowsy bee, only the sound lasted but for a fraction of a second.
Nat knew it instantly for what it was.
A bullet!
It struck the rock behind him, and not half an inch from a direct line with his head, with a dull spatter.