The crest of the Ceylon mountains is of stratified crystalline rock, especially gneiss, with extensive veins of quartz, and through this the granite has been everywhere intruded, distorting the riven strata, and tilting them at all angles to the horizon. Hence at the abrupt terminations of some of the chains in the district of Saffragam, plutonic rocks are seen mingled with the dislocated gneiss. Basalt makes its appearance both at Galle and Trincomalie. In one place to the east of Pettigalle-Kanda, the rocks have been broken up in such confusion as to resemble the effect of volcanic action—huge masses overhang each other like suddenly-cooled lava; and Dr. Gygax, a Swiss mineralogist, who was employed by the Government in 1847 to examine and report on the mineral resources of the district, stated, on his return, that having seen the volcanoes of the Azores, he found a "strange similarity at this spot to one of the semi-craters round the trachytic ridge of Seticidadas, in the island of St. Michael."[1]
1: Beyond the very slightest symptoms of disturbance, earthquakes are unknown in Ceylon: and although its geology exhibits little evidence of volcanic action (with the exception of the basalt, which occasionally presents an appearance approaching to that of lava), there are some other incidents that seem to suggest the vicinity of fire; more particularly the occurrence of springs of high temperature, one at Badulla, one at Kitool, near Bintenne, another near Yavi Ooto, in the Veddah country, and a fourth at Cannea, near Trincomalie. I have heard of another near the Patipal Aar south of Batticaloa. The water in each is so pure and free from salts that the natives make use of it for all domestic purposes. Dr. Davy adverts to another indication of volcanic agency in the sudden and profound depth of the noble harbour at Trincomalie, which even close by the beach is said to have been hitherto unfathomed.
The Spaniards believed Ceylon to be volcanic; and ARGENSOLA, in his Conquista de las Malucas, Madrid, 1609, says it produced liquid bitumen and sulphur:—"Fuentes de betùn liquido y bolcanes de perpetuas llamas que arrojan entre las asperezas de la montaña losas de açufre."—Lib. v. p. 184. It is needless to say that this is altogether imaginary.
Gneiss.—The great geological feature of the island is, however, the profusion of gneiss, and the various new forms arising from its disintegration. In the mountains, with the exception of occasional beds of dolomite, no more recent formations overlie it; from the period of its first upheaval, the gneiss has undergone no second submersion, and the soil which covers it in these lofty altitudes is formed almost entirely by its decay.
In the lower ranges of the hills, gigantic portions of gneiss rise conspicuously, so detached from the original chain and so rounded by the action of the atmosphere, aided by their concentric lamellation, that but for their prodigious dimensions, they might be regarded as boulders. Close under one of these cylindrical masses, 600 feet in height, and upwards of three miles in length, the town of Kornegalle, one of the ancient capitals of the island, has been built; and the great temple of Dambool, the most remarkable Buddhist edifice in Ceylon, is constructed under the hollow edge of another, its gilded roof being formed by the inverted arch of the natural stone. The tendency of the gneiss to assume these concentric and almost circular forms has been taken advantage of for this purpose by the Singhalese priests, and some of their most venerated temples are to be found under the shadow of the overarching strata, to the imperishable nature of which the priests point as symbolical of the eternal duration of their faith.[1]
1: The concentric lamellar strata of the gneiss sometimes extend with a radius so prolonged that slabs may be cut from them and used in substitution for beams of timber, and as such they are frequently employed in the construction of Buddhist temples. At Piagalla, on the road between Galle and Colombo, within about four miles of Caltura, there is a gneiss hill of this description on which a temple has been so erected. In this particular rock the garnets usually found in gneiss are replaced by rubies, and nothing can exceed the beauty of the hand-specimens procurable from a quarry close to the high road on the landward side; in which, however, the gems are in every case reduced to splinters.
Laterite or "Cabook."—A peculiarity, which is one of the first to strike a stranger who lands at Galle or Colombo, is the bright red colour of the streets and roads, contrasting vividly with the verdure of the trees, and the ubiquity of the fine red dust which penetrates every crevice and imparts its own tint to every neglected article. Natives resident in these localities are easily recognisable elsewhere, by the general hue of their dress. This is occasioned by the prevalence along the western coast of laterite, or, as the Singhalese call it, cabook, a product of disintegrated gneiss, which being subjected to detrition communicates its hue to the soil.[1]
1: According to the Mahawanso "Tamba-panni," one of those names by which Ceylon was anciently called, originated in an incident connected with the invasion of Wijayo, B.C. 543, whose followers, "exhausted by sea-sickness and faint from weakness, sat down at the spot where they had landed out of the vessels, supporting themselves on the palms of their hands pressed to the ground, whence the name of Tamba-pannyo, 'copper-palmed,' from the colour of the soil. From this circumstance that wilderness obtained the name of Tamba-panni; and from the same cause also this renowned land became celebrated under that name."—TURNOUR'S Mahawanso, ch. vi. p. 50. From Tamba-panni came the Greek name for Ceylon, Taprobane. Mr. de Alwis has corrected an error in this passage of Mr. Turnour's translation; the word in the original, which he took for Tamba-panniyo, or "copper-palmed," being in reality tamba-vanna, or "copper-coloured." Colonel Forbes questions the accuracy of this derivation, and attributes the name to the tamana trees; from the abundance of which he says many villages in Ceylon, as well as a district in southern India, have been similarly called. (Eleven Years in Ceylon, vol. i. p. 10.) I have not succeeded in discovering what tree is designated by this name, nor does it occur in MOON'S List of Ceylon Plants. On the southern coast of India a river, which flows from the ghats to the sea, passing Tinnevelly, is called Tambapanni. Tambapanni, as the designation of Ceylon, occurs in the inscription on the rock of Girnar in Guzerat, deciphered by Prinsep, containing an edict by Asoka relative to the medical administration of India for the relief both of man and beast, (Asiat. Soc. Journ. Beng. vol. vii. p. 158.)
The transformation of gneiss into laterite in these localities has been attributed to the circumstance, that those sections of the rock which undergo transition exhibit grains of magnetic iron ore partially disseminated through them; and the phenomenon of the conversion has been explained not by recurrence to the ordinary conception of mere weathering, which is inadequate, but to the theory of catalytic action, regard being had to the peculiarity of magnetic iron when viewed in its chemical formula.[1] The oxide of iron thus produced communicates its colouring to the laterite, and in proportion as felspar and hornblende abound in the gneiss, the cabook assumes respectively a white or yellow hue. So ostensible is the series of mutations, that in ordinary excavations there is no difficulty in tracing a continuous connection without definite lines of demarcation between the soil and the laterite on the one hand, and the laterite and gneiss rock on the other.[2]
1: From a paper read to the Royal Physical Society of Edinburgh by the Rev. J.G. Macvicar, D.D.