1867.J CLARK 3IATJRITIFS. 189 



and not far from this spot is a mountain consisting in great part of a 

 soft aluminous stone, of a greyish colour. A road cut along the side 

 of this mountain exhibits in this stone a number of concentric rings 

 from one to twenty feet in diameter, coloured with oxide of iron. 



The most extraordinary feature, perhaps, in the Geology of Mau- 

 ritius is a double-headed mountain adjoining the range which sepa- 

 rates the districts of Grand Port and Flacq. This is about a thou- 

 sand feet high, and the heads are rounded in a very remarkable 

 manner. It consists entirely of hexagonal prisms, from one to five 

 feet in diameter, composed of aluminous rock, of a light greenish 

 grey, with minute black spots. It is so soft as to be easily cut with 

 a chisel or saw. 



The facility with which this stone is wrought induced some 

 persons to employ it for a time ; but it is not suited for building- 

 purposes, as it crumbles away very rapidly under the action of the 

 atmosphere. 



In various parts on the coast of Grand Port may be seen masses 

 of columnar basalt, the prisms of which vary in diameter from six to 

 fifteen inches ; these have evidently been detached from the '* Lion " 

 Mountain, at the foot of which they lie. One such mass, of sixty or 

 eighty tons' weight, is to be seen on the side of a mountain at least 

 two miles from any similar formation. 



In many places a mass of molten stone has been poured down on 

 a bed of clay, itself overlying a stratum of stone. 



In the north-eastern part of the island is a spot comprising an area 

 of ten or twelve square miles, called " la Plaine des Eoches." This 

 is covered almost entirely by a band of rock, generally becoming 

 thinner towards the sea, where it is from six to ten inches in thick- 

 ness. This stratum lies on a bed of loam of about equal thickness 

 with itself. Its surface bears the appearance of water rippled by 

 the wind. In many spots there occur spaces of some hundreds of 

 square feet without a fissure, forming what are locally and aptly 

 called *' paves." In other spots conical mounds are observed, 

 varying in size and height, which have evidently been formed by 

 some upheaving force exerted in the centre, whence radiate cracks 

 extending to the circumference. Such mounds are often seen in 

 other parts of the country, but are nowhere so frequent as on this 

 spot. They offer most convenient stones for building, the upper and 

 lower surfaces being parallel, and a little breaking at the edges 

 being all that is required to prepare them to form symmetrical walls. 

 They are largely employed in the wall skirting the railway. 



The fertile soil beneath this great extent of rock enables trees 

 and grass to flourish wherever a fissure admits their seeds : and in 

 some places cane-holes are broken through the overlying stone ; and 

 the plantations made there thrive well in wet seasons. This part of 

 the country ofi'ers numerous other proofs of the disturbance of the 

 upper strata by subterranean forces. 



Oxide of iron in pisiform nodules occurs in many spots, and was 

 thought of sufiicient importance to cause the establishment of foun- 

 dries by Governor Labourdonnais. These supplied a great portion 



p2 



