41 



p. 12. The laminae being inclined inwards, in disrupting by their own weight fall some feet 

 in front of the base, where a long mound of earth has consequently aceumulated. 



I have now only to revert to the grooves. The circumstances attending them which any 

 hypothesis of their origin must explain are these: their general prevalence ; the existence , 

 however , of exposed rocks devoid of them ; their being commonly confined to the sides 

 facing the exteriour of the Island, although sometimes found on other and even on all sides 

 of a rock; their great depth and regularity ; their general coincidence with divisional lines; 

 their conformity to the course of rain; and their antiquity. It is this last circumstance which, 

 presenting at the outset a great difficulty, leads , on further consideration , to what I con- 

 sider the true explanation. That meteoric influences have been the great agents of erosion 

 I have already suggested. Bat the antique , permanent, character which is impressed on the 

 great majority of the rocks, their vegetable coatings , the hardness and sharpness of the 

 external edges of the grooves , and the absence of all indications of the process of excava- 

 tion being at present in progress , prove that the rocks must have existed under very diffe- 

 rent conditions from the present , to enable atmospheric forces to produce resul ts of such 

 magnitude. The considerations which have hitherto occupied us in the concluding portion 

 of this paper appear to me to indicate what those conditions were. The composition and 

 structure of the external rocks, unveiled by the action of the sea on the beach, shew 

 zones of soft rock (1), rows of globular decomposing masses, and of harder ferruginous 

 spheroids etc. susceptible of being detached, and a general tendency to perpendicu- 

 lar division. If, therefore , we conceive the external layer of the Island, when it first 

 became exposed to decomposition , to have resembled in character the zone that has been 

 laid open for our inspection along the beach , it is easy to comprehend how the wasting 

 away of the more decomposable parts might at last leave exposed masses, including bands 

 of the less stubborn material already partially softened or disentegrated underground , and 

 that the action of the atmosphere and rain torrents would gradually excavate the more yield- 

 ing porlion unlil the solid remnants exhibited their present shapes. 



The grooved and striated rocks of Europe are by some geologists supposed to have been 

 caused by the action of the great and rapid waves called waves of translation induced by 

 the sudden elevation of 1he sea bed and loaded with detritus. Now although in Singapore 

 there is ample evidence of violent movements in the position in which we now find the 

 stratified rocks (2) , we can hardly conceive the Pulo Ubin rocks to have been subjected to 



(1) Some rocks may be seen along the beach with chasing 2 or 3 feet wide, the sides being quite hard and 

 the bottom a soft decoruposed substance- In such cases a zone of rock differing in composition from that adjoin- 

 ing has evidenlly been gradually decomposed and washed out. 



(2) The nearest point at which this displacement can be observed is in the vicinity of Singapore Toten, about 

 eleven miles to the south west of Pulo Ubin. But the whole intermediate country is broken up in the same roan- 

 ner , so as to present the appearance , in many places , of a tempestuous sea , and the billowy hills are throughout 

 so connected and similar, that there can be uo doubt that the forces wtiich elevated them operated during the same 

 period over a wide area, including the southern portion of the Peninsula and its outlying Ai chipelagoes. This 



22 ste DEEL. 1847. F. 



