The march through the jungles and forests, the scant fare, fatigue, and consequent suffering, resulted in sickness. Smallpox and dysentery attacked the land division. Thorns had also penetrated the feet and wounded the legs of many of the people, until dreadful ulcers had been formed, disabling them from travel. In the course of two days’ journey we found six abandoned canoes, which, though unsound, we appropriated and repaired, and, lashing them together, formed a floating hospital. Four miles below Nakanpemba, as we were gliding down at the rate of 1½ knot per hour, we heard the dull murmur of rapids, and from the opposite bank eight canoes were seen to dash swiftly down river, disappearing most mysteriously from view. There being no necessity for us to seek acquaintance with people who appeared to think it undesirable, we did not attempt to disturb them, but, clinging to the left bank, cautiously approached the rapids of Ukassa. These were caused by a ledge of greenish shale, mixed with iron-stone and pudding rock, projecting from the Ukassa hills on the right bank. The hospital was warned in-shore, while I dropped down as near as possible to the rapids and there landed. The land division was requested to encamp for the day abreast the rapids while, selecting ten stout young fellows, in addition to the boat’s crew, I proceeded to explore along the river; but before departing, I gave the strictest orders to Frank and Manwa Sera that upon no account should any one be permitted to move from camp until I returned. The rapids were parted by a couple of long rocky islets running parallel and separated from each other and the left bank by two narrow streams, which descended into a quiet, creek-like portion of the river after a fall of 10 feet within half a mile, but on the eastern side the river was of a breadth of 800 yards, and descended with a furious whirl for the distance of a mile and a half, where it was joined by the quiet flowing creek on the left or western side. We continued our inspection of the shore and river for about two miles, where we very nearly fell into an ambuscade. In a little creek, hidden by high overhanging banks, densely clothed, were some forty or fifty small canoes, the crews all seated, silent, and watching the river. We instantly retreated without disturbing their watchful attitude, and hurried to camp. On arriving at the boat I was alarmed at hearing that Frank had permitted Manwa Sera, the chief, and five others, to detach two of the hospital canoes, and to descend the great rapids. As this was a suicidal act, I felt my blood run cold, and then recollecting the ambuscade in the creek, I lost no time in selecting fifty men and retracing our steps.