299 
coast, and in the centre of the island, is not less than 1500 
feet high. 
* The whole island appears to be one solid mass of trap. 
There is no variety. The rock is of a bluish colour in the 
recent fracture, and thickly interspersed with crystals of 
olivine. The rolled fragments, when broken, sometimes 
exhibit drusy cavities lined with zeolite. The mountain- 
masses are disposed in thick strata, or beds, forming a con- 
siderable angle with the horizon. Even the loose fragments, 
where they have not been displaced by the operations of 
agriculture, are often arranged with surprising regularity; 
And we can trace in them an approximation to the prismatic 
figure. Their upper and lower sides are flat, and the circum- 
ference of from three to six, but generally five, faces. In 
some parts of the island, we meet with tesselated patches, a 
quarter of a mile in extent, consisting of a smooth sheet of 
tock, cracked into these prismatic fragments, and so nicely 
adjusted to each other, that room is barely left for a line of 
verdure in the fissures to mark their division. 
^ In the faces of the deep ravines through which most of 
the rivers have worked their channels, the rocks occasionally 
display the columnar form of basalt: exhibiting both the 
Perpendicular and the horizontal section, as well as the angles 
of the columns. In other parts, where this regularity does not 
Prevail, we may observe the prismatic masses lying over each 
other, but separated by the intervention of a layer of earth, 
the product, apparently, of their own decomposition. In the 
same manner they stretch out into the sea or omy’ side of 
the island, giving a solid base to those coralline fabrications 
which are generally believed to compose the whole reef: ; though 
itis more probable, that they only form the superficial crust. 
" The soil of Mauritius is a tenacious earth of a ferrugi- 
Rous colour, mixed with a very small proportion of vegetable 
mould. In the dry season, it becomes extremely hard, - 
‘racks into numerous fissures. In some parts of the - 
X is sufficiently plastic to admit of being manufactured — 
Sort of bottles called Gargoulettes, which possess the | 
estimable quality of preserving water, at a tem 
