SENEGAL, colony of French West Africa (q.v.) bounded on the north by Mauritania (q.v.), west by the Atlantic, south by Portuguese Guinea and French Guinea, and east by the Faleme, which separates it from the colony of French Sudan (q.v.). Wedged into Senegal and surrounded by it save seawards is the British colony of the Gambia. The colony of Senegal has an area of 192,00o square kilometres and a pop. (1933) of 1,619,944 (density 8.43 per square kilometre) of which 6,90o are Europeans.
The coast extends from the mouth of the Senegal to Cape Roxo, where the Portuguese frontier begins. The only gulf on the coast is that which lies to the south of Cape Verde and contains the island of Goree (q.v.). The coast in the northern part is low, arid, desolate and dune-skirted, its monotony relieved only here and there by cliffs and plateaux. Farther south it becomes marshy, and clothed with luxuriant vegetation. A little to the north of the Gambia the coast-line is much broken by the archipelago of islands formed by the Salum estuary, whilst south of the Gambia is the broad estuary of the Casamance. Be tween the Senegal and the Gambia and as far east as about 13° W., the country behind the seaboard is a slightly elevated and, for the most part, barren plain. Farther east is a mountainous and fertile region with altitudes of over 4,000 feet. The moun tains sink abruptly towards the Niger valley, while southwards they join the Futa Jallon highlands. On the north they extend to the left bank of the Senegal and throw out spurs into the desert beyond. The Senegal (q.v.), its tributary the Faleme, and the upper course of the Gambia (q.v.) are the chief rivers which drain the country. The Salum, already mentioned, is a river-like estuary which penetrates fully 1 oo m. and is split into many channels. It is navigable from the sea for 6o miles. The Casamance flows between the Gambia to the north and the Cacheo to the south, and has a drainage area of some 6,000 square miles. Rising in the Futa Jallon, the river has a course of about 2 1 2 m., and at Sedhiu, 105 m. from the sea, is 1 m. broad. The mouth of the river is fully 6 m. wide. Six to seven feet of water cover the bar at low tide, the river being navigable by shallow draught vessels for the greater part of its length.
The low region of the seaboard consists of sand stones or clay rocks and loose beds of reddish soil, containing marine shells. At certain points, such as Cape Verde and Cape Roxo (or Rouge), the red sandstones crop out, giving to the latter its name. Clay slates also occur, and at intervals these sedimen tary strata are interrupted by basaltic amygdaloid and volcanic rocks. For instance the island of Goree is basaltic. The base of the mountains is formed in certain places of clay slate, but more generally of granite, porphyry, syenite or trachyte. In those dis tricts mica-schists and iron ores occur. Iron and gold are found in the mountains and the alluvial deposits. Many of the valleys are covered with fertile soils; but the rest of the country is rather arid and sterile.
Climate.—There are two seasons, the dry and the rainy, the latter contemporaneous with the European summer. In the rainy season the wind blows from the sea, in the dry season the har mattan sweeps seaward from the Sahara. Along the seaboard the dry season is cool and agreeable; in the interior it is temperate in the three months which correspond to the European winter, for the rest of the year the heat is excessive. The maximum readings (90° to ioo° F), which are exceptional at St. Louis, become almost the rule at Bakel on the upper Senegal. The mean tem perature at St. Louis is 68° to 7o° F. The rainy season begins at Goree between the 27th of June and the 13th of July. During this period stornis are frequent and the Senegal overflows and floods the lowlands.
The principal tree is the baobab (Adan sonia digitata), which sometimes at the height of 24 ft. has 'a diameter of 34 and a circumference of 104 feet. Acacias are numerous, one species, A. adansonia, being valuable for ship timber. Among the palm-trees is the ronier, whose wood resists moisture and the attacks of insects; in some places, as in Cayor, it forms magnificent forests. The mampatas grows sometimes too ft. high, its branches beginning at a height of about 25 feet. Landolphia and other rubber plants, and the oil-palm, grow lux uriantly in the Casamance district. The karite, or shea-butter tree, is common. Wild indigo is abundant, and the cotton plant is indigenous.