"Of all the strange things, did you ever hear such a terrible groaning before, Dick?" asked Roger. "I wonder if it has anything to do with the noise we caught before, that was so like thunder." "Hardly, for that was surely far away, while this is close by," replied the other boy, with a puzzled look on his sun-browned face. Roger even took off his foxskin cap, as though he imagined that the dangling flaps which he used to keep his ears warm in bitter weather might interfere with his sense of hearing. Again those strange groanings made themselves heard. This time both boys managed to locate the sound as coming from the right. That was at least one point gained, and it was toward that quarter they now turned their attention. If they had been trying to pick out the most difficult spot in all the wild vicinity, they would have selected that toward which their attention was now directed. The rocks seemed to be piled on one another in hap-hazard fashion. Here and there they formed deep chasms, the sides of which were so precipitous as to be incapable of being scaled by any creature short of a monkey. "It comes welling up out of the ground itself, Dick," ventured Roger, presently, with awe in his manner, as though, after all, he might be wondering whether there could be any truth in the tales told of the Evil Spirit that haunted these weird ridges, speaking in thunder tones at one minute, and with dreadful groanings the next. Dick believed in taking the bull by the horns in a case like this. "We must look into it, Roger; it would never do for us to say we had been driven away through hearing some mysterious sound that we did not understand." "There it comes again, Dick, and louder than before. What can it be?" "The hot spring seemed to tell of some sort of fires away under the surface of the ground," the other said, reflectively, "and it might be that this is more of the hot vapor pressing up through holes in the rocks." "But how like human groans the sounds are!" marveled Roger. "I agree with you," his companion returned, "but have you forgotten the time we heard those terrifying noises coming from the old mill that stood a mile away from our homes, and how some of our companions fled, but we had the hardihood to go inside and look around?" "Yes," interjected Roger, quickly, "and we found the wind forced a way through a crack between two logs, and made the doleful noise! It may be something like that here." "We will soon know, because I mean to make my way over there and take a good look around," announced Dick. "If you go I will keep you company!" declared Roger, just as stoutly, as he gave a glance down, in order to make sure that the powder in the pan of his flint-lock rifle had not been disturbed, and that the weapon was ready for instant use.