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] [Footnote 1: From a paper read to the Royal Physical Society of Edinburgh by the Rev.J.G.Macvicar, D.D.] [Footnote 2: From a paper on the Geology of Ceylon, by Dr.Gardner, in the Appendix to Lee's translation of RIBEYRO'S _History of Ceylon_, p, 206.

The earliest and one of the ablest essays on the geological system and mineralogy of Ceylon will be found in DAVY'S _Account of the Interior of Ceylon_, London, 1821.

It has, however, been corrected and enlarged by recent investigators.] The tertiary rocks which form such remarkable features in the geology of other countries are almost unknown in Ceylon; and the "clay-slate, Silurian, old red sandstone, carboniferous, new red sandstone, oolitic, and cretaceous systems" have not as yet been recognised in any part of the island.[1] Crystalline limestone in some places overlies the gneiss, and is worked for oeconomical purposes in the mountain districts where it occurs.[2] [Footnote 1: Dr.Gardner.] [Footnote 2: In the maritime provinces lime for building is obtained by burning the coral and madrepore, which for this purpose is industriously collected by the fishermen during the intervals when the wind is off shore.] Along the western coast, from Point-de-Galle to Chilaw, breccia is found near the shores, from the agglutination of corallines and shells mixed with sand, and the disintegrated particles of gneiss.