184/.] including Notices of Sumatra, the Malay Peninsula, tyc. 537 



small opaque white specks. Within the glass, the igneous rock, for a 

 narrow space, was finely vesicular, and violet-coloured like veins and 

 some grains of the sandstone were scattered through this band. The 

 opaque spots in the glass were evidently included grains of sand semi- 

 fused at their edges. This specimen is identical in character with some 

 products of proper volcanoes. In the slopes to the west of Bukit 

 Temah, which are covered with thick beds of clays and sands, included 

 layers, composed of fragments of torrified granite, occur. 



Many of the islands and rocks near Singapore exhibit most decisive 

 proofs of volcanic convulsions. Thus in a reef of sandstone rocks 

 lying between the Island of Blakan Mati and Pulo Sikijang, a black 

 ferruginous rock has been obtruded as a lava through seams and fissures 

 in the sandstone, and at some places has spread over that rock and 

 boiled up above it, assuming fantastic shapes, the sandstone is altered 

 by heat in the same manner as the rock is often seen to be in Singa- 

 pore.* Basalt and greenstone are found on Pulo Ooban, which lies 

 close to the north-east coast of Singapore. Similar rocks of various 

 structure and character, compact, vesicular, &c. with claystone, porphy- 

 ries and other volcanic minerals, are brought from Islands in the neigh- 

 bourhood to Singapore to be used for the foundations of houses. The 

 original production of the latter rocks must of course be referred to 

 an epoch long anterior to that of the former, which undoubtedly cor- 

 responds with that of the Singapore semi-volcanic rocks. 



We are therefore, I think, justified in considering Singapore and the 

 neighbouring Islands to have been the seat of volcanic convulsions 

 spread over a considerable area, if nowhere of great intensity. There 

 are many reasons, but not strictly local, to believe that their date was 

 in a late era of geological time. The subject however is a difficult one, 

 and there is not room for its full discussion in this paper. I may here 

 only mention amongst the local facts tending to the above conclusion, 

 the softness of some of the rocks which have not been altered by vol- 

 canic action, but have been elevated and greatly stretched or drawn out, 

 contorted or compressed in the process ; the absence of any superficial 

 changes not due to atmospherical causes since the time of their eleva- 



* Mr. Thomson describes to me an analogous injection ol si reddish-black substance, 

 lateriticin its appearance, into the fissures of a block of granite on the north coast ol 

 Buitang-. This 1 shall describe on procuring- a specimen, if F do not visit the localitj 



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