It is only on the sea-coast that we have an opportunity of viewing the materials which constitute the mass of this island, every other part being covered with soil. We here see nothing but granite. This granite, however, as will be seen by the specimens, is of different structure from that of Prince of Wales’ Island, and the other varieties we had observed. In many masses it is almost a pure feldspar, finely crystallized and excessively hard. In other parts we find narrow veins of gneiss traversing masses of the granite; and in other parts the granite assumes a porphyritic appearance, containing, imbedded, numerous small nodules of gneiss.
In this vicinity, the great continental chain of mountains gradually diminishes in altitude, occasionally offering considerable interstitial distance between their summits, which now become more rounded as well as of lower elevation, whilst the whole chain bends more towards the south-east, leaving an extensive flat land between its base and the sea. This flat tract, however, is yet somewhat elevated above the sea, and at several points, particularly on its oceanic border, as at Parcelar Hill and Rachado Point, rises into solitary, isolated hills, of a conical shape, rounded at top, but of inconsiderable height. The general features of the country had now altered considerably; the hilly eminences are probably constituted of sandstone or clay slate. The country is everywhere covered with wood to the water’s edge.
On examination, we found the small hills about this place, and the substratum of soil generally, to consist of a compact, nodular iron-shot clay, used commonly in building. In its geologic locality it is soft and easily cut into oblong masses like large bricks, which become very hard by exposure to the air. The old and now ruined fort, the Portuguese church, &c., are built of this material. It is very heavy, and appears to contain a large proportion of iron. This substance is common in Ceylon, and on the Malabar coast, it is used for building and for making roads. It is there known by the name of kabouc. No other mineral was here observable. In Ceylon it is found towards the base of the mountains, in the vicinity of granite rocks.