﻿326 PROCEEDINGS OF THE GEOLOGICAL SOCIETY. [June 25, 



East Sikijang about 35°, or from 45° to 80° E. ; in the range ter- 

 minating at Tanjong Batu (Singapore) about 85°, or from 50° W. 

 to 45° E. 



A high inclination being very common, a decided tendency to a 

 dip in one direction is not to be anticipated. In several localities the 

 rocks dip away from vertical on both sides, indicating the existence 

 of synclinal axes, which in a few instances are seen, as in the N.E. 

 point of Blakang Mati, Mount Palmer, &c. The only distinct anti- 

 clinal axis that I have observed is in a hill forming the south point 

 of West Sikijang, where the strata are arched. 



Notwithstanding this tendency to verticality, the westerly dip on 

 the whole predominates in the western part of the district, for, 

 although beds having an easterly dip are found in P. Mirambong, 

 P. Blakang Padang, P. Busong, P. Jong, P. Sabaru, the Batu Blyer 

 Range, P. Hantu, Blakang Mati, Sikukur, West and East Sikijang, 

 T. Pinger, Mount Wallich, Mount Palmer, Kiltiney Hill (34), &c, 

 and in some cases the dip is exclusively to the east, yet in most of 

 these localities the beds that dip to the east are associated with a 

 greater extent of beds that have a westerly dip. In the eastern part 

 of the district, however, the dip is generally to the eastward, as at 

 the Tikongs, Tanjong Pungai, and the N.E. point of Bintang; but 

 it is not uniformly so, for at Tanjong Lompatan it is about 45° W. 

 In the next considerable exposure of rocks on the east coast, those of 

 Sidili Point, to the north of the district, the dip is again easterly. 



The strata, although where iron-rock and quartz occur often much 

 disturbed, and sometimes in patches, broken up and mixed, forming 

 a hard ferruginous breccia, are nowhere completely shattered, and 

 the fragments confusedly mingled, except in considerable portions of 

 Government Hill (34), Mount Sophia (48), and Mount Siligi (47), 

 where no beds are distinguishable, the hard sandstone being scattered 

 through the clay, at some places in angular blocks from a few inches 

 to several feet in diameter, and in others as a fine breccia. 



2. The Plutonic rocks. — The prevalence of felspar and hornblende 

 renders these rocks very decomposable when kept exposed to the in- 

 fluence of water under ground. Hence while blocks rising above the 

 soil suffer little waste, the mass below is almost everywhere converted 

 into clay to a considerable but unknown depth. The only locality in 

 the district where rocks have escaped decomposition in sufficient 

 number and size to display their structure is Pulo Ubin. This has 

 probably been owing to the steepness and narrowness of the range of 

 which it consists, and the action of the sea along both its sides, which 

 have combined to degrade and wash away the decomposed portions, 

 thus leaving the more resistent masses to emerge from the soil and 

 stand out above the influence of decomposition*. 



All the numerous exposed blocks of Pulo Ubin have a large laminar 

 or zoned structure. The laminae are in different forms, flat, spheri- 

 cal, and concentric, and variously curved ; but the systems of circles 



* When an exposed rock is attacked, the decomposing portion is washed or falls 

 off, and the decomposition is arrested for the time. Under-ground decomposition 

 tends to spread unchecked on all sides. 



