46 
nal structure. ‘The greater number are of solid rock, of a 
bluish-gray colour and extreme hardness, in some instances 
homogeneous, in others exhibiting crystals of hornblende, 
felspar, and olivine, sparingly scattered, or forming more 
than a moiety of the compound mass. Between these, are 
frequently interposed beds of scoria, cohering from the effect 
of partial fusion; of tufa, studded with crystals of augite; or 
of ashes, condensed by the pressure of the superincumbent 
mass. The latter, still retaining in a great measure their 
friable nature, moulder gradually away, and leave the more 
compact strata in projecting shelves. 
The mountain appears to have been rent asunder by 
some violent convulsion, and the fissures filled up by a hard 
stony mass, of a bluish or reddish colour, and of the nature 
of trap, forming regular veins, the ramifications of which 
can be traced by the eye to a great height in the face of the 
rock. The sides of these veins, where they come in contact 
with the rock, are invariably in a semi-vitrified state, and 
exhibit obscure marks of crystallization. Along the north- 
west side of the island there runs a belt of low land, about 
six miles long, varying from a quarter of a mile to a mile in 
breadth, and presenting to the sea a perpendicular front, 
from 50 to 300 feet high. The whole of this plain is a con- 
fused assemblage of stony fragments, scoria, and other vol- 
canic products, resting on a bed of lava. All these matters | 
are in a progressive state of disintegration, and the greater 
part of them reduced to mere nuclei imbedded in their con- 
stituent elements in the state of a black indurated earth. 
* The northern extremity of the plain is, in a great mea- 
sure, cleared of its wood. By setting fire to the grass, the - 
trees have been so far scorched as to destroy their vegeta- 
tion, but they still lie strewed along the ground, and it 
will cost some labour to remove them. The rest is yet ina 
state of nature, covered with an impenetrable copse. 
* The surface of the plain, though apparently smooth and 
even, while clothed with its native herbage, is in fact 
extremely irregular, being everywhere broken by small 
ridges of loose stones, concealed under a mere scurf of soil. 
