the Siberian Balkash, apparently a great inland sea, in reality a shallow expansion of the River Ili.
The coastline is clearly defined only at the northern extremity, where the Saharian sands drifting before the trade winds have been heaped up in dunes, whose base projects like a headland into the water. Almost everywhere else it seems impossible to say where the Fig. 170. — Lake of Tuburi.
land ceases and the water begins. The south-east corner, and farther north the part near the Kanem coast, are occupied by groups of islands, covering, according to Nachtigal, one-third of the whole surface, and separated from each other by shallow or marshy straits. The southern archipelago of Karka is in fact a mere assemblage of eminences dotted over a morass, which if drained would present an appearance analogous to that of the neighbouring land of Kanem, where green hills and leafy thickets alternate with treeless spaces.
Besides the rains, which begin in June, Tsad is fed by large tributaries, chiefly from Bornu in the west, and from Baghirmi in the south. From Bornu come two komodogu or "rivers," which in the dry season shrink to a mere chain of Jagoons, but which during the rains flow in a continuous stream much too deep te if, tore and rapid to be forded. The Yeu (Yoobé of Nachtigal, Waubé of Barth), has its farthest sources in Haussa Land, 480 miles to the west, and it drains the whole of West Bornu, and apparently also the Babir territory on the Adamawa frontier, which is said to send it a tributary flowing for part of its course through an underground gallery.
Much more important are the contributions received from the southern regions watered by the copious tropical rains. The streams, such as the Mbulu, rising in the Mandara country, flow sluggishly over the level plains, expanding into vast
