Tchad

or Chad, a lake in the central part of the African Sudan. Kamerun, French Sahara, and British Nigeria meet here. The lake has several tributaries but no outlet. The greatest length is about 140 miles. During the rainy season the lake has an area of about 30,000 square miles, but in dry weather it shrinks to less than one-quarter of that area, the border being occupied by vast marshes. There are numerous islands inhabited by negroes. Unlike the Aral, the Great Salt Lake, and other inland bodies of water having no outlet, the waters of Lake Tchad are fresh. It is believed that the salt brought down by the tributaries of the lake escapes through some underground outlet.