68 1 On the Local and Relative Geology of Singapore. [July, 



The transformed and partially transformed sedimentary hill ranges 

 rest, I conceive, upon granitic bubbles* where the plutonic action has 

 been loss intense. The fissures and cracks formed by the pressure of 

 these bubbles have been the channels, the gases given off from their 

 surface the immediate agents, of all the alterations. The tracts where 

 only granite now appears swelling above the surface had previously 

 passed through the same stages. In other words laterite is one of the 

 earliest stages in the reduction of the upper rocks superincumbent on 

 a plutonic sea into the substance of which that sea is composed. 

 Where the heat has been least intense, the upper rocks have merely 

 been raised, — where greater, lateritic, scoreous, and other partially 

 altered, hill ranges, have been produced. A higher degree of plutonic 

 action has produced quartzo-ferruginous ranges like that of Cape 

 Rachado. The highest degree has transformed or reduced the whole 

 into granite and allied crystalline rocks, from the mode in which the 

 granites, &c. come to the surface at Singapore, we see that the whole 

 region there has been broken up by the plutonic sea below. I can 

 proceed no further however at present, and must close this rough 

 draught of my ideas. 



the superincumbent rock as well as upraising and fracturing 1 it. A great fissure would 

 probably be produced when it reached a certain nearness to the surface. As it slowly 

 pressed up it would appear as in (fig. 2), but as it became exposed to the atmosphere, it 

 would have an increased tendency to solidify at the surface, and as it rose above the 

 level of ad, (fig. 3), it might already have a semi-solid shell sufficient to prevent the 

 already thickening mass within from swelling out laterally over the surfaces ab, cd; 

 but suppose it was sufficiently viscid to do so, the consequence would be that the spaces 

 oo (fig. 4), would be exposed to an intense heat on two sides and be reduced in a more 

 or less crystalline form to a portion of the bubble. I believe that granitic bub- 

 bles always swell up with exceeding slowness, and that the centre of the bub- 

 ble (if its base be of great size) may remain for centuries, or even longer, in a 

 viscid state, while a thick solid crust of granite has formed on the sides and summit, and 

 that the central part will still exert as slow upward and outward pressure as it solidifies, 

 and may itself be subject to a long continued elevatory pressure from the sea below- 

 Ln other words the summits of granitic mountains and minor masses may go on rising 

 above the base, after the latter with the whole surface has solidified, and when the base 

 has no further upraisd movement save what it may possess in common with the plutonic 

 sea below. Great dislocations in the upper crust must necessarily result, but does not 

 every plutonic mountain range bear witness to such dislocations 1 I must refer to my 

 paper on Pulo U'bin for the facts on which these veins are based. 



• I do not mean that each base or hill range has a corresponding protuberance on the 

 surface of the plutonic base, but that the whole system of hills and hillocks has been 

 produced by unequahtiea in that surface and by the directions which the principal and 

 divergent lines of fracture have taken. 



