shape
existing in our formations. Let our correspondent observe the caution
thus given, in reading the latest attempt at summing up the main facts
in the geoloy of this island, contained in the account of Ceylon given
by Mr. J. F. Dickson in the new edition of the Encyclopedia Britatmica. Scattered
in various periodicals, especially in the transactions of the local
Asiatic Society, are a number of interesting papers by Dr. Kelaart on
upcountry laterite, by the late Mr. Oswald Brodie on salt formations,
and, of special value a more complete and more correct list of the
minerals of Ceylon than that of Gygax, by Mr. Alexander Dixon. This
recent and careful observer saw no trace of coal in any shape, although
he noticed slight indications of tin and copper. As yet, however, our
only economic mineral of consequence is plumbago, of which in its
purest carbon form the island has almost a practical monopoly. Dr.
Trimen, in a paper on the botany of Ceylon, glances at some interesting
theories connected with its old-world geological history. In this
sketch we have not, of course, included all fugitive articles or chance
wrtiters on the geology of Ceylon, and we were about to claim that we
thought we had omitted no work or writer of importance, when we
recollected the " Circular Notes " of that most accomplished but
perhaps somewhat imaginative geologist, ths late Mr. Campbell of Islay.
Such
generally being the information available, we may add that the accepted
theory is that the dynamic forces which originally raised Ceylon "from
out the azure main" are still at work and that a slow, very slow
process of upheaval is going on. We cannot tell what the rocks are "
all the way down," or to the centre of our globe, but our obvious
foundation rock is primitive granite. It is not only our lowest but our
highest formation, for It has in some places been so projected as to
form the rocky domes and pinnacles of nature's temples on our mountain
tops. Granite, grey and red, with porphyry and sienite, occasionally
occur amongst our most prevalent formation, gniess, which overlies the
granite. The igneous rock, according to the received theory, pushed up
the stratified rock, gneiss, from the ocean in which it had slowly
formed, the gneiss in its turn pushing up beds of crystalline limestone
(dolomite), which bad formed, also in the ocean, over the surface of
the gneiss. These are our three principal and primitive rocks, gneiss
being king of all. Indeed, some have held the view that true granite
where in contact with its allied rock, has been compelled to enter on
the metamorphic processes, which have given gneiss such protean shapes,
colours, and conditions. While granite is being metamorphosed into
gneiss at one end of the scale, gneiss decaying from the action of the
atmosphere on superabundant felspar, is, at the other forming new
combinations, and giving us the valuable laterite locally known as
cabook (sometimes called iron clay); good as blocks for building
purposes, as gravel for road material, and as it is further acted on by
the atmosphere and man's agency, the foundation of our most fertile
soils. The characteristics of this curious product of gneiss will be
thoroughly discussed and settled before the discussion on its failure
as a foundation for the Maligakanda reservoir closes. We may just
notice in passing that while the red colour produced by peroxide of
iron distinguishes some of our very richest soils, oxides of iron in
other shapes are charged with the strangely contrasted barrenness which
distinguishes our upland patanas (mountain prairies or savannahs) from
the rich forests from which they are in most cases so sharply divided.
The superabundant iron in Ceylon was formerly utilized by the natives,
many furnaces and much slag being scattered over the land, but now the
imported metal has put an end to all local manufacture. Felspar,
besides leading to the decay of gneiss and its transmutation into
laterite, is the origin of the beds of kaolin or China clay, pretty
common in our hill system, and also of the very pretty but not
intrinsically valuable moonstone, with its semi-pearly lustre. The more
kaolin in the rock, the more potash in the soil. When coffee was our
great cultivation the quantity of lime contained in our gneiss-derived
soils was deemed deficient, either for fertilizing purposes or for
keeping the clay soils mechanically free. But for
