MEKONG, or Me Nam Kong (pronounced Kawng), sometimes known as the Cambodia River, the great river of Indo-China, having its origin in the Tibetan highlands. It is the third or fourth longest river in Asia and the seventh or eighth in the world. It is about 2800 m. in length, of which 1200 flow through portions of the Chinese Empire and Tibet and 1600 through French territory. Its sources are not definitely settled, but it is supposed to rise on the slopes of Dza-Nag-Lung-Mung in about 33° N., 93° E., at an altitude of 16,700 ft. above sea-level. Throughout the greater part of its course in Tibet, where it is called the Dza-Chu, it flows south-eastwards to Chiamdo, on the great east and west caravan route from China to Lhasa. At this point it is about 10,000 ft. above sea-level. From here it flows southwards through little-known mountain wastes. Below Dayul in lat. 29° it is known by the Chinese name of Lantsan Kiang. For the next 300 m. of its course the Lantsan Kiang, or, as it soon becomes known among the Thai peoples inhabiting its rugged valley, the Mekong, is very little known to us. The river flows beneath bare and rocky walls. A few scattered villages of Lusus and Mossos exist in this region; there is no trade from north to south. In 25° 18′ N. the Tali-Bhamo caravan route, described by Colborne Baker, crosses the river by one of those iron suspension bridges which are a feature of Yun-nan, at a height of 4700 ft. above sea-level. From this point to Chieng or Keng Hung, the head of the old confederacy of the Sibsawng Punna or Twelve States, it is little known; the fact that it falls some 900 ft. for each degree of latitude indicates the character of the river. Under the provisions of the Anglo-French agreement of January 1896, from the Chinese frontier southwards to the mouth of the Nam Hok the Mekong forms the frontier between the British Shan States on the west and the territories acquired from Siam by France in 1893. By the treaty of 1893, from that point southwards to about 13° 30′ N. it is also the frontier between French Indo-China and Siam, and a zone extended 25 kilometres inland from the right bank, within which the Siamese government agreed not to construct any fortified port or maintain any armed force. This 25 kilometre neutral zone was abolished in 1905 when France surrendered Chantabun to the Siamese, who in their turn ceded the port of Krat and the provinces of Melupre and Bassac, together with various trading concessions to France on the right bank of the Mekong. Below the Siamese Shan town of Chieng Sen the river takes its first great easterly bend to Luang Prabang, being joined by some important tributaries. This portion is obstructed by rapids. The country is mountainous, and the vegetation of the lower heights begins to assume a tropical aspect. From Luang Prabang the river cuts its way southwards for two degrees through a lonely jungle country among receding hills of low elevation. From Chieng Khan the river again turns eastwards along the 18th parallel, forcing its way through its most serious rapid-barrier, and receiving some important tributaries from the highlands of Tung Chieng Kum and Chieng Kwang, the finest country in Indo-China. In 104° E. the river resumes a southerly course through a country thinly peopled. At Kemarat (16° N.) the fourth serious rapid-barrier occurs, some 60 m. in length, and the last at Khong in 14° N. From here to its outfall in the China Sea the river winds for some 400 m. through the French territories of Cambodia and Cochin China, and to its annual overflow these countries owe their extraordinary fertility. The French have done much to render the river navigable. Steamers ply regularly from Saigon through Mytho to Pnompenh, and launches proceed from this place, the capital of Cambodia, to the Preapatano rapids, and beyond this a considerable portion of the distance to Luang Prabang, the journey being finished in native boats.  (J. G. Sc)