On the Local and Relative Geology of Singapore, [July, 



myself of the natural vertical sections afforded by the shores of Singa- 

 pore, and the smaller Islands, into which the southern extremity of the 

 Peninsular range is broken, and was thus soon in possession of a body 

 of facts which gave a certainty and consistency to the above veiws. I 

 minutely examined the Islands of Pulo Brani, Blakan Mati, Sikukur, 

 and Sikijang on the one side, and Pulo l/bin, Pulo Tikong, Bcesar, Pulo 

 Tikong Kcchil, Sejalrat Bcesar and Kcchil, &c. on the other side. I 

 also explored the neighbouring coasts of the Peninsula, and the banks 

 of the Johore river. The result was that I found the foregoing hypo- 

 thesis, so far as it had been developed, to be substantially an expres- 

 sion of the facts. It had however given too much prominence to some 

 modes of the volcanic or semi-volcanic action, and too little to others. 

 Thus, although there has been a certain degree of eruption in some 

 cases where the gases in forcing their way to the surface have excited 

 an unusual mechanical force, their action has, in general, been limited 

 to a partial reduction and metamorphosis of the rock in the zones or 

 dykes through which they have passed up [or in those larger tracts 

 beneath which the surface of the plutonic sea has risen to such high 

 subterraneous levels that the whole superincumbent matter has been 

 saturated by its exhalations. I have also noticed several facts which 

 appear to require us to believe that some portions at least of Singapore, 

 were under water at the time when the gaseous action first reached the 

 surface. The vast abundance of hydrated peroxide of iron and the 

 mode in which ancient ferruginated breccias and conglomerates some- 

 times occur, would be most simply explained by this hypothesis. The 

 circumstances adverted to in the paper on this subject must be borne 

 in mind. In some places a considerable quantity of matter derived 

 from the hills has been deposited in the intervening valleys, probably 

 at or soon after the time of elevation, and been subsequently covered 

 up by modern sea mud on which mangroves have rooted and spread.] 



The most difficult branch of the enquiry has been the relation 

 between the volcanic action to which the sedimentary rocks have been 

 subjected, and the crystalline rocks which are associated with them. 

 But, disregarding this for the present, and considering the volcanic 

 action apart from any hypothesis of its origin or its relations, and 

 reasoning from its visible effects, we may lay down this position abso- 

 lutely, that the whole region in question (and a much wider one, as it 



