With regard to the existence of metallic veins in the mountains of Ceylon almost nothing is known. Traces of tin
have lately been said to have been met with; and it is not at all
unlikely that it may hereafter be met with in greater abundance, as it
is principally in the metamorphic rocks that metallic veins are found
to exist, and mostly in mountainous countries or their immediate
neighbourhood. As their existence however cannot be predicted, further
knowledge concerning them will only be obtained by actual examination
of those parts of the island most likely to possess them.
It
is often asked if there is any chance of coal being found in Ceylon.
Although from all that is yet known of the geology of the island, the
chances are very much against any thing like a true coal formation
being met with, yet it would not be safe to give a decided answer on
the subject; for, unlike the carboniferous beds of England, which have
in general" one or more systems of stratified rocks intervening between
them and the gneiss, those of the north of India
were found by Dr. Royle to rest on the Gneiss itself. This much,
however, is certain, that whenever Gneiss forms the uppermost rock,
coal need never be looked for, as it is well known that in all parts of
the world, the series of rocks which form the crust of it, hold a
regular and undeviating-relative position to each other, and_ hence,
the upper rock of any country being given, a Geologist can tell with
the greatest certainty what system or systems of rocks will never be
found beneath it.
The
nature and origin of laterite or kabuk, which is so common on the west
side of the Island, have given rise to much diversity of opinion. Some
have supposed it to be a volcanic production, and others a deposition
from water; but I have most completely satisfied myself that it owes
its existence to neither of these causes, but to the simple decay of
Gneiss rocks. I was first led to this view from the examination of a
cut through a knoll on the road from Galle to Belligam, and afterwards
from others on the road between Colombo and Ambepusse, and in numerous
instances of the same nature in the Central Province. In many of these
cuts there is no difficulty |in tracing a continuous connection,
without any definite lines of demarcation, between the soil and the
laterite on the one hand, and the laterite and the solid rock on the
other. In no part of the world, save in the Peninsula of India, have I
witnessed a like decomposition of Gneiss, and this renders it probable
that the cause is due to some peculiarity in the chemical nature of the
rock itself
As
in almost every other country where the Gneiss system prevails,
immense deposits of -crystalline lime-stone are found in various parts
of the interior of the island, overlying the Gneiss. Thus, it is well
known to occupy a large space in the valleys of Kundasala, Matale and
Peradeniya at the latter place, and between it and Kandy, being
extensively converted into lime for building purposes. This like all
other lime-stone strata has evidently been formed by aqueous chemical
deposition from an ocean which overlay the Gneiss, and its highly
crystalline structure is probably owing to the same heat which partly
fused the Gneiss itself previous to its solidification. It is not
simply a carbonate of lime, but contains besides a considerable
quantity of carbonate of magnesia, and to such combinations the name of
dolomite is given. It is still undecided by Geologists whether the
magnesia of such rocks was originally contained in the solution from
which they have resulted, or from the action of heat on the rocks with
which they are connected, and which as is the case with Gneiss, arc
known to cantain a certain proportion of Magnesia.
Passing
over all those series of rocks to which the names of secondary and
tertiary have been given, none of which are known to exist in Ceylon,
we come to those very modern ones called post-tertiary, which are being
formed at the present day, and which either shew themselves in the
shape of elevated terraces of shells, or in a more solid form arising
from the agglutination of particles of sand and fragments of such
corallines and shells as still inhabit the surrounding seas. Such
elevated shell banks, and such rocks are to be
