small,
it is highly probable more may yet be found to reward the
mineralogist, who may search in the quarries of the interior, where it
is broken for making lime.
SKETCH OF THE GEOLOGY OF CEYLON:
By George Gardner, F. L. S.
(From " Ribeyro's Ceylon," by George Lee.)
The
island of Ceylon appears, at an early period of its physical history,
to have formed the southern extremity of the peninsula of India. This
opinion is confirmed both by its position and its geological
constitution. At the present period the narrow channel which separates
them is only a few feet in depth, and I believe I shall be able to
prove that the whole of Ceylon is gradually rising above the sea
level, and that consequently the time, geologically speaking, is not
far distant when the island will again become united to the continent.
Tradition, indeed, records that the passage was at one time not only
broader but much deeper than it now is, and this led to the survey
which preceded the deepening of the Pamban passage.
The
island is about 270 miles long, by about 145 in breadth. It is of an
ovate form, and its extremities point nearly due south and north. It is
broadest at its southern extremity, and it is in that direction that
the greatest mass of high land exists. The great central mountain range
rises, for the most part, rather suddenly out of a broad belt of flat
country that stretches between it and the sea, and which varies from
twenty to sixty or eighty miles in breadth, but towards the north,
north-west, and north-east, the flats are much broader than in any
other direction. The general direction of the mountain chain is from
south to north, but it is much broken up, and intersected by beautiful
broad, and fertile valleys, varying from one to six thousand feet above
the level of the sea. The mountains themselves vary from 3,000 to 8,280
feet, the latter being the elevation of Pedrutalagala, a round..-J dome
which overlooks the valley of Nuwara Eliya on the one side and that of
Maturata on the other. The peaks which come next to this one in point
of elevation are Kirigal-potta, to the south of it, which is 7,810
feet; Totapella, to the eastward, which is 7,720 feet; and Adam's Peak,
which for a long period was considered, as it still is by the natives,
to be the highest, of all, 7,420 feet. Taking their rise in these
mountains, and traversing the valleys, are, of course, a number of
streams of various sizes. The largest of these is the Mahaweliganga—
the Ganges of Ptolemy—which has its origin near the summit of
Pedrutalagala, and, after a very tortuous course of nearly 200 miles,
ultimately falls into the sea near Trincomalee, on the north-east side
of the island. Three or four other streams of considerable size empty
themselves on the west coast.
Although
the geological st/ucture of the Island is very simple, it offers
notwithstanding much that is interesting to the geologist. The series
of rocks are but few in number. The lowest, which is also the most
common, is that to which the name of gneiss is given. In some places it
is overlaid by extensive beds of Dolomitic lime-stone; and on some
parts of the coast that very modern formation known by the name of
Breccia is found to exist. The clay slate, silurian, old red sand
stone, carboniferous, new red sand-stone, oolite, and chalk systems,
which form such remarkable features in the Geology of England, have not
yet been met with in Ceylon, nor is it at all probable that any of them
ever will be found, as the island has now been traversed in all
directions without any traces of them having been seen.
Gneiss
rocks are the lowest of that division to which the name of stratified
is given, in contra-distinction to those which show no traces of strati-
