The formation of the subsoil is mostly sandstone bearing a ruddy sand. The surface is in rare places a brown vegetable humus, extending but a few inches in depth, or more generally a hard yellow-reddish ferruginous clay covered with quartz nodules of many colours, and lumps of carbonate of lime, or white and siliceous sand, rather resembling a well-metalled road or an “untidy expanse of gravel-walk” than the rich moulds which belong to the fertile African belt. In many parts are conical anthills of pale red earth; in others ironstone crops out of the plain; and everywhere fine and coarse grits abound. The land is in parts condemned to perpetual drought, and nowhere is water either good or plentiful. It is found in the serpentine beds of nullahs, and after rain in ziwa, vleys, tanks, pools, or ponds, filled by a gentle gravitation, and retained by a strong clay, in deep pits excavated by the people, or in shallow holes “crowed” in the ground. The supplies of this necessary divide the country into three great districts. On the east is Marenga Mk’hali, a thick bush, where a few villages, avoided by travellers, are scattered north and south of the road. The heart of the region is Ugogo, the most populous and the best cultivated country, divided into a number of small and carefully cultivated clearings by tracts of dense bush and timberless woods, a wall of verdure during the rains, and in the hot season a system of thorns and broomwork which serves merely to impede a free circulation of the air. These seams of waste land appear strange in a country populated of old; the Arabs, however, declare that the land is more thinly inhabited than it used to be. Mgunda Mk’hali, the western division, is a thin forest and a heap of brakey jungle. The few hills are thickly clothed with vegetation, probably because they retain more moisture than the plains.