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PROCEEDINGS OP THE GEOLOGICAL SOCIETY. [June 25, 



and, during the north-east monsoons, the heavy waves from the China 

 Sea piled it up in long belts in front of the mangroves. 



The clayey sediment of the plutonic tract now accumulated more 

 exclusively around the mangroves within these belts. As the sands 

 extended, the waves no longer penetrated into the inlets. In the 

 higher part of the valleys, and in the recesses of the lower parts, the 

 water became brackish, the mangrove and its associates died out, and 

 a new and more exuberant order of vegetation, in which palms and 

 ferns abounded, took their places. A black peaty matter now formed 

 rapidly, filling up all the hollows, spreading over the ancient mud- 

 flats, and burying the remains of the mangrove-forests. The alluvium 

 now advancing beyond the inlets into the gradually shoaling bay of 

 Singapore, the three processes which we have described proceeded for 

 the future simultaneously. One sand-bank after another was thrown 

 up, and the streams from the valleys were deflected into lagoons be- 

 tween them, in which a succession of events analogous to that of the 

 old inlets took place. In the upper part of each successive lagoon 

 were brackish marshes, in which dense forests grew ; and in the lower, 

 and along the margins of the creeks as far as the water was salt, the 

 mangrpves kept their place, forming, with the sand, a barrier against 

 the waves. Bank after bank arose, lagoon after lagoon was formed, 

 until the whole of the ancient bay was converted into a marsh, covered 

 with forest and containing a succession of dry banks of sand or per- 

 matangs, the last of which has formed the present lagoon of the Ge- 

 lang, projecting its extremity, like a tongue, into the harbour of Sin- 

 gapore at Tanjong Ru (Sandy Point), and has given a common estuary 

 to the streams from every valley that opens into the Singapore 

 plain. 



Thi§ history we narrate with as much confidence as if there had 

 been human witnesses and chroniclers of its whole progress, because 

 not only has it left its own records of all its stages, but its current 

 events are repetitions of these, and afford the fullest explanation of 

 each of them*. 



The valleys have now perfectly level surfaces, covered with forest 

 where plantations have not been formed; and the layers of which 

 they are composed are the pure plutonic clay, — a dark bluish marine 

 clay which is seen at the heads of the valleys on both sides of the 

 island up to the foot of Bukit Timah, — a black, soft, vegetable peat, 

 or rather mud, in some places of great depth where hollows have 



* " The lower parts of the valleys are mostly swampy, consisting of sand, clay, 

 and black peaty mud ; of the latter there are considerable tracts constantly moist 

 and exhibiting an extraordinary rankness of vegetation. Looking on one of these 

 swamps covered with tall but slender trees, and dense underwood growing up 

 rapidly, and from the looseness of the deep bed of black vegetable matter, — the 

 accumulated remains of their short-lived predecessors — destined soon to fall in 

 their turn, and considering the deposits of clay and sand which accompany and 

 give rise to it, it is impossible to doubt that we see nature repeating the precise 

 process by which the materials of most of the ancient carboniferous strata were 

 brought together. Towards the sea these forest marshes give place to mangrove 

 swamps." — On the Local and Relative Geology of Singapore, including Notices of 

 Sumatra, 8fc. (by J. R, Logan, Esq.), Journ. Beng. Asiatic Society, vol. xvi. p. 525. 



