AND THE NEIGHBOURING ISLANDS. I53 



alluvial matter, for several miles inland, and the gradual retirement of the 

 ocean indicated by ridges running- parallel to the present line of coast. 

 The process of conversion of such a hard material as granite into alluvial 

 matter is distinctly seen on the road to the Great Hill, in the small valley 

 between " Mount Olivia" and the " Highlands of Scotland." The pre- 

 cipitous bank, about sixty or seventy feet in height, presents a mass of 

 red clayey sand, used generally in lieu of gravel for repairing the roads, 

 which is merely decomposed granite as seen in the specimens Nos. 

 55 and 50, taken from the spot. Notwithstanding this alluvial origin, 

 no organic remains, not even shells, have been found hitherto imbedded 

 in any part of the valley. Query — may not this be accounted for, 

 by the small number of animals which inhabit the island, and by the 

 paucity of shells now in existence along the coast? The indigenous 

 animals are principally birds and insects, and on two tours round the 

 island, I did not discover in all one hundred shells on any part 

 of it. 



The soil of the valley is various. Near the point it is sandj% Avith 

 a surface of about four inches of vegetable mould from decayed leaves 

 and branches of trees. In advancing about a mile into the interior, 

 the ground begins to rise, and the superficial stratum is also a light 

 vegetable mould, about a foot in thickness, resting on the sand. Near 

 the foot of the mountains, the soil becomes rich in many places, and 

 beds of white clay resembling fuller's earth, are found here and there, 

 more especially in Vulo Ticoose bay. In those parts of the island, 

 near the sea coast, which are generally overflowed and thickly covered 

 with mangrove, ( Rliizophora) the soil for a foot in lliickncss is a rich 

 black mould. Tliroii^hoiit the island it is li^lil, ;\iul in most [)arts is 

 composed of clay, \miU a large portion of sand, wlaih renders it 

 very porous. 



