"I know it, Dick, but my nature is different from yours. I am either bubbling over with joy or else weighed down with foreboding. But we can see some distance ahead at this point, and I must confess that there is no sign of a human being, so Jasper and his comrades cannot be returning along the trail." "The wind is shifting for one thing," observed Dick, "which may bring about a change in the weather before very long." "Listen, what do you suppose that sound can be? If the weather were not so cold, and the season summer instead of early winter, I would surely say it was distant thunder!" All three stood still to listen intently. Presently the far-away rumbling sound was again borne to their ears; and, just as Roger had declared, it was like distant thunder coming from beyond the range of forest-clad hills. It was not strange that the two boys and the frontiersman turned uneasy looks upon each other, surrounded as they were by such strange freaks of nature. CHAPTER IX SURROUNDED BY MYSTERIES "WHAT about the swivel gun in the camp; could it be heard as far away as this, do you think, Dick?" asked Roger, as though a new idea had flashed into his mind. The other shook his head in the negative. "Hardly," he replied, "and, even if it were possible, you forget that it is only when the wind picks up from this new quarter that we hear the sound." "And that is from the northwest, while our camp lies back yonder, more in the northeast," admitted Roger. "I admit that, when I spoke, I was picturing a horde of half-naked Indians trying to carry the camp by storm, and Captain Clark rallying his defenders behind the breastworks we built out of pine logs and earth." "It is nothing of that sort, I am sure," said Dick, "though, when you ask me to explain the origin of that sound, I am as much in the dark as you." "Well, as our way lies toward the northwest," remarked Roger, "there's some satisfaction in knowing we will be getting closer to the mystery all the time." "I am glad to see that you are not afraid, Roger." "There can be no telling what state I may be in before we get out of this strange country," admitted Roger, laughingly. But Dick knew him too well to think he could show any sign of fear. Mayhew said little, for he was naturally a man of few words. He could not be reckoned as above the average of his class; and possibly there was a well-defined streak of superstition in his nature, even as it was to be found in other bordermen of the day. Left to his own devices, perhaps Mayhew would have much preferred not to advance any further into this unknown and terrifying land. He had no particular desire to learn whether the stories told were true or false; and the camp that had been left behind held many alluring claims to his regard.