There were four windows--two at the front and two at the rear--all of the same shape and size. There was but the single door, of which so much has already been said, and therefore the lower portion of the building could not be made safer. The stone chimney, so broad at the base that it was more than half as wide as the side of the outside wall, was built of stone, and rose a half-dozen feet above the roof. It was almost entirely out of doors, but was solid and strong. "If the Indians were not such lazy people," said Melville--looking earnestly at the broad fire-place, in front of which stood the new-fashioned stove--"they might set to work and take down the chimney, but I don't think there is much danger of _that_." He had hardly given expression to the thought when he fancied he heard a slight noise on the outside, and close to the chimney itself. He stepped forward, and held his ear to the stones composing the walls of the fire-place. Still the sounds were faint, and he then touched his ear against them, knowing that solid substances are much better conductors of sound than air. He now detected the noise more plainly, but it was still so faint that he could not identify it. He was still striving hard to do so when, to his amazement, Dot called him from above-stairs-- "Where are you, Mel? Is that you that I can hear crawling about over the roof?" CHAPTER FIVE A STRANGE VISIT--OMINOUS SIGNS Melville Clarendon went up the short stairs three steps at a time, startled as much by the call of his sister as by anything that had taken place since the siege of the cabin began. As he entered the room he saw Dot sitting up in bed, and staring wonderingly at the shivered window-glass, particles of which lay all around. "Oh, Mel!" said she, "papa will scold you for doing that; how came you to do it?" "It was the bad Indians who fired through the window at me, and I fired at them: you were sleeping so soundly that you only half awoke; but you must keep still a few minutes longer." "I thought that was you on the roof," she added, in a lower voice. That there was someone overhead was certain. The rasping sound of a person moving carefully along the peak of the roof was audible. The lad understood the meaning of that which puzzled him when on the lower floor: one of the warriors was carefully climbing the chimney--a task not difficult, because of its rough uneven formation. The significance of such a strange act remained to be seen. It appeared unlikely that any of the Sioux were daring enough to attempt a descent of the chimney; but that such was really his purpose became clear within the following minute. The Indian, after making his way a short distance along the peak, returned to the chimney, where, from the noises which reached the listening ones, it was manifest that he was actually making his way down the flue, broad enough to admit the passage of a larger body than himself.