GAMBIA, a large river of West Africa, and the only river of Africa navigable by ocean-going boats at all seasons for over 200 m. from its mouth. It rises in about 11 ° 25' N. and 12° 15' W., within r 5o m. of the sea on the north-eastern escarpment of the Futa Jallon highlands. Although the distance from the source to the mouth of the river is little more than 30o m. in a direct line, the length of the stream owing to its serpentine course is about i,000 m. It flows first N.N.E., receiving many left-hand tributaries, but about 12° 35' N. takes a sharp bend N.W. and maintains this direction until it leaves the fertile and hilly region of Bondu. The descent to the lower district is marked by the Barraconda rapids, formed by a ledge of rock stretching across the river. From the Barraconda rapids to the Atlantic the Gam bia has a course of about 35o m. Throughout this distance the waters are tidal. At Yarbatenda, a few miles below Barraconda, the river has a breadth, even at the dry season, of over 30o ft., with a depth of 13 to 20 ft. From the falls to McCarthy's island, a distance of 200 m., the river valley, which here presents a park like appearance, is enclosed by low rocky hills of volcanic char acter. For 5o m. below the island, where the stream is about Boo yds. wide, the banks of the river are steep and thickly wooded. They then become low and are fringed with mangrove swamps. From Devil's Point, a sharp promotory on the north bank, the river widens and enters the Atlantic, in about 131° N. and 162° W., by a broad estuary. Near the mouth on the south side is St. Mary's island (32 m. long by 12 broad), and opposite is Barra Point, the river being here contracted to 22 m. Eighteen miles lower down the distance from shore to shore is 27 m. There is a sand-bar at the entrance to the river, but at the lowest state of the tide there are 26 ft. of water over the bar. Vessels draw ing 13 ft. can ascend to McCarthy's island and those drawing 6 ft. to Barraconda all the year round. The Gambia is in flood from June to November, when the Barraconda rapids can be passed by small boats, while above the rapids the stream is navigable for 16o m. Politically the Gambia is divided between Great Britain and France—Britain possessing both banks of the river up to, but not including, Yarbatenda.
The Gambia was one of the rivers passed by Hanno the Car thaginian in his voyage along the west coast of Africa. It Was known to Ptolemy and the Arabian geographers, and was at one time supposed to be a mouth of the Nile, and, later (18th century), a branch of the Niger. It was possibly visited by Genoese navigators in 1291, and was certainly discovered by the Portu guese c. 1446, but was first explored for any distance from its mouth by the Venetian Alvise Cadamosto, who pub lished an account of his travels at Vicenza in 1507 (La Prima Navigazione per l'Oceano alle terre de' Negri della Bassa Ethi opia) . Afterwards the Gambia became a starting-place for ex plorers of the interior, among them Mungo Park, who began both his journeys (1795 and 1805) from this river. It was not until 1818 that the sources of the Gambia were reached, the discovery being made by a Frenchman, Gaspard Moiiien, who had travelled by way of the Senegal and Bondu. The middle course of the river was explored in 1851 by R. G. MacDonnell, then governor of the Gambia colony, and in 1881 Dr. V. S. Gouldsbury also navigated its middle course. No native craft of any kind was seen above Barraconda.