34 Mauritius, paet i. 



M. Bory St. Vincent has described similar calcareous beds 

 over nearly the whole of the plain of Pamplemousses. 

 Near Port Louis, when turning over some large stones, 

 which lay in the bed of a stream at the head of a pro- 

 tected creek, and at the height of some yards above the 

 level of spring tides, I found several shells of serpula 

 still adhering to their under sides. 



The jagged mountains near Port Louis rise to a 

 height of between 2,000 and 3,000 feet; they consist 

 of strata of basalt, obscurely separated from each other 

 by firmly aggregated beds of fragmentary matter ; and 

 they are intersected by a few vertical dikes. The 

 basalt in some parts abounds with large crystals of 

 augite and olivine, and is generally compact. The 

 interior of the island forms a plain, raised probably 

 about a thousand feet above the level of the sea, and 

 composed of streams of lava which have flowed round 

 and between the rugged basaltic mountains. These 

 more recent lavas are also basaltic, but less compact, 

 and some of them abound with feldspar, so that they 

 even fuse into a pale coloured glass. On the banks of 

 the Great Eiver, a section is exposed nearly 500 feet 

 deep, worn through numerous thin sheets of the lava of 

 this series, which are separated from each other by beds 

 of scorias. They seem to have been of subaerial forma- 

 tion, and to have flowed from several points of eruption 

 on the central platform, of which the Piton du Milieu 

 is said to be the principal one. There are also several 

 volcanic cones, apparently of this modern period, round 

 the circumference of the island, especially at the 

 northern end, where they form separate islets. 



The mountains composed of the more compact and 

 crystalline basalt, form the main skeleton of the island. 

 M. Bailly l states that they all ' se developpent autour 

 1 ■ Voyage aux Terres Australes,' torn. i. p. 54. 



