the
other side, towards the land, the rock commonly terminates in sand, the
beach generally rising above it. This bed is in most places distinctly
stratified, and where (he strata are not deranged by fractures and
subsidences, they are quite horizontal. The appearance of the rock is
not uniform : its principal varieties are a yellowish-grey sandstone,
another almost black, and a third of the first kind, but containing
nodules of the latter. These varieties' occur in the same stratum, and
a vertical section often exhibits successive layers of the two first
kinds. They all consist of sand agglutinated by carbonate of lime,
which, from its texture, appears to have been deposited from water.
Thus the stone crumbles to pieces, and is reduced to sand when heated
before the blow-pipe or immersed in an acid. The proportion of
carbonate of lime is variable, being from 26'5 to II per cent. The
larger the proportion, the harder is the sandstone; thus the
last-mentioned is soft and taken from a depth in an incipient state of
formation, while the former is taken from the surface, is completely
formed and extremely hard. Irrespectively of the proportion of
carbonate of lime, the sand of which the stone is formed, is of
different kinds. The sand of the light-coloured variety is chiefly
silicious, consisting of fine water-worn particles of quartz, like the
sand of the shore, and like it, it occasionally contains shells and
pebbles. The sand of the variety nearly black, is a mixture of
silicious particles, and of particles of iron glance becoming magnetic
by wasting. It is extremely hard, the iron no doubt acting the part of
a cement, as well as the carbonate of lime.
The
question of the formation of the sandstone is involved in much of the
same obscurity as that of the limestone of Jaffnapatam, and the same
conjectures might be offered■ respecting the probable cause of the
deposit of the calcareous cement. This instance of the formation of
rock from the dissolved and disintegrated materials of old rocks is not
peculiar to Ceylon, as it is quite as common as those of decomposition
itself. Both the limestone and sandstone of this recent formation may
become very useful. Very good lime may be made of the former, and
serviceable millstones, perhaps of the latter, if it can be found, as
is very probable, of a coarse quality. For architectural purposes both
stones are well adapted, more especially the sandstone for great public
works, as it may be wrought at little expense, and when the wind blows
off the land may be easily shipped.
Mineralogy.
The
mineralogy of Ceylon, is, in some respects, remarkable and curious. The
island is remarkable for its richness in gems, and, so far as has yet
been ascertained for its comparative poverty in the useful metals. It
is remarkable also for the number of rare minerals that it affords,
and for the smal 1 variety of the ordinary species : thus in its
mineralogical character, it accorded with the taste of its late native
rulers, who were more prone to display than any work of utility, to
pomp than profit. Its mineral productions "may be classed under two
heads, those attached to granitic, which constitute the greater part,
and those pertaining to dolomite rock. The only metallic ores that can
be hitherto said to be found in any quantity deserving of notice, are
of iron and manganese. Iron in different forms is pretty generally
diffused, and somewhat abundant. Iron pyrites, magnetic iron ore,
specular iron ore, red hematite, bog-iron ore, and earthy blue
phosphate of iron are all found. Red hematite and bog-iron ore are more
common than the other species. It is from these ores that the natives
extract the metal. With the exception of iron pyrites, magnetic
ironstone and the blue phosphate, the species of iron occur so
frequently in granitic rock or its detritus, as not to require notice.
The first, iron pyrites, is found at Ratnapura, disseminated through a
gn v felspar rock, and in veins of quartz at Mount Lavina on the sea
shore. Magnetic iron ore. is found in masses, imbedded in gneiss in the
vicinity of Kandy and in granitic rocks in Wellassa and Trincomalee.
The earthy blue phosphate of iron is procurable from a marshy ground
near Colombo, and from a bed of bog-iron ore near Kandy. It is said to
be used by the natives as a pigment.
