The Orange river is the only outlet to the sea to convey the water brought down by the ancient river system that drains the south, the central, and the western divisions of this extensive and important portion of the Kalahara desert. The Orange for 250 miles forms the southern boundary. The rivers that drain the north-western and the central part of the Kalahara are the twin streams Nosop and Oup, appropriately called twins, as the two join for twenty miles and again separate, both running parallel to each other within a short distance, entering the Molapo close to the great bend, where that river takes the name Hygap, and flows south, and enters the Orange at Kakaman's drift. The Nosop rises in the Waterberg of Damaraland in two head-waters called the Black and White Nosop, which unite north of Westly Vale and join the Oup at Narukus. The Oup rises in Damaraland in latitude 22 degrees, under the name Elephant river, and gathering the waters of other small branches, joins the Nosop at Narukus for twenty miles, then becomes an independent stream and, as I have stated, falls into the Molapo. Several shallow watercourses traverse the desert, but are not of sufficient importance to merit a description. The other river connected with the above system is the Molapo, which rises on the west slope of the central watershed at an altitude of 5350 feet, in 26 degrees 5 minutes South latitude, 26 degrees 25 minutes East longitude, where a plentiful supply of pure water flows throughout the year, and takes a westerly course to the great bend in latitude 25 degrees 50 minutes East, longitude 21 degrees 16 minutes, when it takes the name Hygap, as already stated, receiving in its course the small streams Moretsane and Setlakoola. The Kuruman river rises in the south of the Kuruman mission station, and with its small tributaries flows west and enters the Hygap below the great bend. The Back river commences in a range of the Brinus mountains, a beautiful and picturesque group, several thousand feet in height, of granite formation, well-wooded in the kloofs and ravines. The peculiar feature of the river is that it has two outlets, one to the east into the Hygap, the other to the west into the Great Fish river. South of this river three mountain streams drain the southern Kalahara, viz. the Nisbet, Aamo, and Keikab, which fall into the Orange to the west of the Hygap. The Great Fish river, which completes the river system of the Kalahara in the Orange river basin, rises in the Awas mountain in Damaraland, 22 degrees 40 minutes South latitude, 17 degrees 30 minutes East longitude, at an altitude of 6400 feet, and flows south for 430 miles, and enters the Orange river ninety miles from its mouth. The country through which it flows is very dry from the scarcity of rain. There are no important streams in the east, but on the west there are many tributaries that drain the high mountain country. The Chun