MAURITIUS, an island and British colony in the Indian ocean (known whilst a French possession as the Ile de France). It lies between 57° 18' and 49' E., and 19° 58' and 2o° 32' S., 55o m. E. of Madagascar. The island is irregularly elliptical— somewhat triangular—in shape, and is 36 m. long and about 23 m. broad. It is 13o m. in circumference, and its total area is about 72o square miles. The island is surrounded by coral reefs, so that the ports are difficult of access.
Dependent upon Mauritius and forming part of the colony are a number of small islands scattered over a large extent of the Indian ocean. Of these the chief is Rodriguez (q.v.), 375 m. E. of Mauritius. Considerably north-east of Rodriguez is the Chagos archipelago, of which the chief is Diego Garcia (see CHAGOS). The Cargados, Carayos or St. Brandqn islets, deeps and shoals lie at the south end of the Nazareth Bank about 25o m. N.N.E. of Mauritius.
From its mountainous character Mauritius is a most picturesque island. The most level portions of the coast districts are the north and north-east, all the rest being broken by hills, which vary from 50o to 2,700 ft. in height. The principal mountain masses are the north-western or Pouce range, in the district of Port Louis; the south-western, in the districts of the Black River and Savanne ; and the south-eastern range, in the Grand Port district. In the first of these, which consists of one principal ridge with several lateral spurs, overlooking Port Louis, are the Pouce (2,650 ft.), and the Pieter Botte (2,685 ft.). The highest summit is in the south western mass of hills, the Black River mountain (2,711 ft.). The south-eastern group of hills consists of the Montagne du Bam bou, with several spurs running down to the sea. In the interior are extensive fertile plains, some 1,200 ft. in height, forming the dis tricts of Moka, Vacois, and Plaines Wilhelms; and an abrupt peak, the Piton du Milieu de l'Ile (1,932 ft.) rises from the centre of the island. Other prominent summits are the Trois Mamelles, the Montagne du Corps de Garde, the Signal Mountain, near Port Louis, and the Morne Brabant.
The rivers are small, and in the dry season little more than brooks, in the wet season, raging torrents. The principal stream is the Grande Riviere, with a course of about 10 miles. The island
is of volcanic origin and the more recent craters (now extinct) cross the centre of the island. The volcanic rocks are all basic in character and belong to two periods of eruption, the earlier forming the mountain mass of the Black River district and the later being basalts and dolerites poured out from craters of the central district. Many of the craters have been partially denuded but some still contain lakes, e.g., Grand Bassin, Mare aux Vacois and Mare aux Joncs. Some lava-flows alternate with coral reefs. The basement rocks are represented by a mass of clay-slates in the Black River mountains and by much contorted chlorite-schists in La Selle mountain of the centre of the island. There is evidence of a recent elevation of from 4o ft. (south) to 12 ft. (north), whilst caves and underground rivers in the lava-flows are common.