At Chiwyu, we camped near the loftiest altitude of the gradual and almost unbroken rise of upland, at a height of 5400 feet. To the northward of Suna and Chiwyu, the country, however, no longer retained that grand unfurrowed uplift, but presented several isolated hills and short ranges, while to the westward also we saw that it was divided into oval basins, rimmed with low hills. From these same hollows and furrows and basins at the base of the hills, scattered to the north and west of Suna and Chiwyu, issue the first tiny rivulets, which, as we continue our journey to the north-west, gradually converge to one main stream, trending towards Lake Victoria. It is in this region, therefore, that the most extreme southern Sources of the Nile were discovered. Since leaving Mpwapwa, we have not crossed one perennial stream. All our drinking water has been obtained from pools, or shallow depressions lately filled by rain. Between Suna and Chiwyu was crossed one small rill flowing north-easterly, which soon afterwards joins another and still another, and gathering volume, swerves north, then north-west. These are the furthest springs and head-waters of a river that will presently become known as the Leewumbu, then as the Monangah, and lastly as the Shimeeyu, under which name it enters Lake Victoria on the south-east coast of Speke Gulf. Descending into the basin of Matongo from Chiwyu with its melancholy associations, we crossed several narrow and shallow furrows, which a few late rains had probably caused, and came to a clear stream flowing north through a deep rocky channel. Near this ravine was a space about a square mile in extent, strangely torn up and exhibiting thousands of boulders and blocks, large and small, with smooth, waterworn tops; and the sides of what is now a small hill in the centre of the basin showed visible traces of the action of furious torrents through centuries of time. The hard granite was worn into cones, the tops of which bore a calcined appearance, proving the effect of intense heat suddenly cooled by rain. The rocky channel of this stream in the Matongo basin was a veritable geological section. The surface consisted of massive granite boulders imbedded in vegetable deposit; below this was a stratum of sand about 3 feet deep, below the sand a stratum of coarse shingle of quartz, feldspar, and porphyry, about 8 feet thick, and below this was alluvium, resting on solid rock.