42 



these movements since their consolidation. The first hurried view of a portion of the masses 

 at the quarries left the impression that the rocks had been shattered and separated by such 

 forces. But I am now satisfied that , with some slight exceptions due to decomposition and 

 consequent alteration in the balance of the different parts of some of the larger rocks , 

 they all occupy their original relative positions , and even their original absolute positions 

 with reference to the horison , although the level of the whole Island and adjacent tract 

 has probably shifted. At all events no violent vilbratory movement has affected the Island 

 since the joints were formed and the raass stood above the surrounding tract. I cannot 

 think that a wave of power adequate for the excavation of the channels could have been 

 generated by a movement which would have left the projecting rocks undisturbed , or even 

 that the force of the wave itself could have met with such resistance from the smaller 

 rocks as to enable it to grave the channels instead of displacing the rocks. No doubt a 

 large proportion of these rocks were formerly firmly wedged into the mass of the Island , 

 but many must have been more or less isolated, as the channels embrace more than 

 one side. The undulations, if any, attending the elevation of the Island and inducing waves 

 of translation (if they were sufficiently violent } and the upheavals sufficiently great) would 

 probably be in the direction of the Peninsula ; and , after the Island and the adjacent 

 hills of Singapore and the mainland rosé above the sea , waves might act on both sides of 

 the Island transversely to the line of undulation. But as the principal fissures and soft 

 bands are in the same direction , the circumstance of the grooves mostly coinciding with it 

 does not peculiarly fovour the application of the wave theory. But in rejecting its applicability, 

 we may, at the same time , allow that the action of the waves , whether ordinary or extra- 

 ordinary, as the Island gradually , or by abrupt steps, rosé above the sea, may have as- 

 sisted to a considerable degree both chemically and mechanically in wearing the channels. 

 On the coast of Singapore opposite the eastern extremity of Pulo Ubin , and only a mile 

 distant , there is a layer of pebbles evidently marking the last step in the elevation of the 

 land. Such pebbles driven to and fro by the waves against the rocky beach of Pulo Ubin 

 would be instrumental in deepening hollows. 



Since a portion of this paper was writ ten I have seen , in the number of the Quarterly 

 Journal of the Geological Society of London for May last , in the Presidents annual address 

 to the Society , a notice of the observations made on the coasts of Sweden and Norway , 

 last year , by M. Durocher. M. Durocher found along a portion of the coast , and par- 

 ticularly in the Islands off it, deep channels and furrows in directions from NW. to 

 SE., some 10 to 20 inches wide and 5 to 10 feet deep, «effects of erosion," says the 

 President , » on a much greater scale than I remember to have read of before." The re- 

 semblance of these channels to those of Pulo Ubin is not confined to their unusual size , 

 but is carried out in the circumstance of the sides of the interiour of many of the channels 

 being grooved in the directions of their longer axes , of their sometimes dividing into two 



tract, I have already said , is probably but a small seclion of a vast region, embracing India on the one side and 

 Jfustralia on the other in which sitnilar forces were in activily during the same period, and produced sitnilar effects. 



