Nevertheless, the march was not devoid of trials and discomforts. The ground was very irregular, and at one point, where the bank of the river rose to a considerable height above the water-level, they found that they had come to a stretch of hard gravel interspersed with large fragments of a whitish rock, making progress very slow and difficult. Looking back, John saw the glow of the fires left burning in the fort--a little patch of red amid deep black. When they descended to grassy land again he stumbled over an obstruction about three feet high, which Bill told him was an ant-hill. A little further on he heard a strange whistling that seemed to come from a line of trees on his left hand. Hearing the men behind gulping, he halted, and got them to exchange loads, listening meanwhile to the weird and mournful sound, which now increased in volume, now died away in a doleful wail. He asked Bill if he recognized the sound as that of an animal, but he replied that he had never heard it before. After a few moments John observed that the sound rose and fell with the gusts of wind, and concluded that it was caused by the breeze sweeping through the trees. He reassured the men; but it was not till long afterwards he discovered the origin of the sound. The trees were a species of thorn about eight feet high, with leafless branches on which hung a number of hollow seed-pods. In these an insect bores a hole, and the wind, passing through the innumerable tiny apertures, produces the musical notes which so much disturbed the negroes. After about two hours, John felt much fatigued. The continued exertion had revived the dull aching pain in his back and limbs, and he thought it prudent to rest awhile. The progress had been so good that he could afford to waste an hour: there would still be time to reach the village before the dawn. The whole party lay down on a grassy knoll, speaking only in whispers. Occasionally the cry of some night-bird broke the stillness, and once there came, from far away, the sharp bark of a hyena. At the end of an hour the safari was again on foot. Twice more John found himself compelled to halt, and after the second time Ferrier persuaded him to let four of the men carry him, in a litter which they quickly made by slinging one of the blankets between two rifles. Always taking the river as guide, they pressed on again. At last, when the sounds of re-awakening life in the trees proclaimed that dawn was at hand, they came to the foot of a long grassy acclivity which John felt sure led up to the village. After a consultation with Ferrier, he decided to wait a little until there was light enough to show them the way clearly. The air was misty, but the blackness of night was passing, and at length they were able to see the goal of their long march--the "bad men’s" village, lying in perfect stillness on the hill-top.