or **Tsad**, Lake, a large sheet of water in Central Africa, lying between N. Lat. 12° 30' and 14° 30', E. Long. 13° and 15°; bounded by the native states of Bornou, Kanem, Begharmi, and others. Its length from N. to S. is about 120 miles, and its breadth varies from 60 to 80. Reports of such a lake had been current for some time, when Clapperton and Denham in 1823 first ascertained its actual existence, and explored a great part of its coast. Further information was obtained by Overweg and Barth, who arrived in Kuka in 1851. Overweg embarked at Madiari near Kuka, on the lake, in a small boat, which they had brought across the desert for that purpose, and for some distance from the shore he had to make his way through narrow channels among a number of small islands. Leaving these, he crossed a large expanse of open water, and reached another group of small islands, inhabited by a people called Biddumas. On account of a war between these people and some neighbouring tribes, Dr Overweg was unable to reach the eastern shore of the lake, and had to return by the same route as he came. Further explorations were carried on by Dr Vogel in 1854. The water of Lake Tchad is quite fresh, and its depth is in general very small, being only from 8 to 15 feet. At different periods, however, it undergoes great changes, sometimes falling so low that the channels between the islands are left dry, and at other times rising so high as to cover some of the islands and overflow the flat country about the shores. The open part of the lake called *Inkibul*, "white or open water," by the natives, only occupies the south-western part of its centre. The whole of the coasts are skirted by a multitude of small islands, and the north and east portions are occupied by a similar group. The lake has no outlet, and it receives, besides a number of smaller streams, the Shary from the south and the Yeo from the west. The former of these rivers is large and navigable; the latter is partially dry for some months in the year. Fish abound in the lake, and turtles, crocodiles, elephants, and hippopotamuses on its shores. Large wild boars, gazelles, antelopes, and buffaloes are also numerous, but lions and leopards are more rarely seen. The Biddumas, who inhabit the islands, are an independent nation, by no means in a very savage condition. Many of the islands are densely peopled. The people have also boats of considerable size, propelled by long poles instead of oars or sails.

**TCHAÜSSY**, a town of the Russian empire, in the government and 25 miles E.S.E. of Moghilev. It contains Roman Catholic and Greek churches, a synagogue, and a convent. A large annual fair is held here. Pop. 4772.