Not so much in the things they said, but in the manners of their speech. They were blinking in the sunlight.
They camped out early in the evening, at the first area they came upon, with enough room, not wanting to chance being on this trail after dark with no place to turn. If he could discover that the indians, hearing in some way of the coming train, had determined to lay in wait for its coming by a certain point, by knowing where they would place their ambush, he could flank them and thus put there at fault.
I thought it would be amusing.