﻿1851.] 



LOGAN — GEOLOGY OF SINGAPORE. 



335 



from their decay will be principally characterized by their profusion 

 of snch pebbles and blocks. 



5. The upheaval of the sedimentary rocks was in general attended 

 with great violence, as is shown by the irregularity in the strike and 

 dip of the beds in numerous circumscribed localities, and the breaking 

 up and mingling of those in Government Hill, &c. Where there are 

 most evidences of violence, there is the greatest development of iron 

 or quartz. The line of disturbance, for instance, which goes through 

 Government Hill, and is continued in the hill south of it, ending in 

 Tanjong Malang or Batu, is marked in the latter by iron-masked 

 blocks and gravel on the surface, sandstone indurated and pervaded 

 by an iron-honeycomb, iron-mammillated crusts on the sides of the 

 beds, &c, and in Government Hill by the clayey beds adjacent to 

 the disrupted sandstone being converted into the typical laterite, and 

 by the sandstone at some places near the junction being broken into 

 a mass of small fragments recemented by iron and clay*. 



6. The formation and intumescence of the plutonic rocks of the 

 district caused this upheaval, and gave the prevailing direction to the 

 stratification and to the ranges of hills, this direction agreeing with 

 that of the plutonic zone of the Peninsula. 



7. The partial metamorphosis, induration, and ferrugination of the 

 sedimentary strata were effects of this plutonic action. 



8. The vast abundance of iron evolved during the plutonic intu- 

 mescence, and rising into the strata, is the distinguishing peculiarity 

 of the Malayan zone of elevation t, and its wide-spread effects so 

 strongly strike the eye that the other changes are less observed ; but 

 the latter evince even more decidedly the potency and the unity of 

 the elevatory agent, and are particularly worthy of attention as assi- 

 milating that agency to the more common kinds of plutonic meta- 

 morphosis. The soft strata in some places have been converted into 

 Lydian stone, porcellanite, clay-slate, hornblende slate, steatite, and 

 chert. If we extend our observations a little beyond the district, we 

 find similar changes on a much greater scale. Thus the eastern coast 

 of Pulo Krimiin Kichi (Little Carimon), which rises only eighteen 

 miles to the west of the last of our sandstone islets in that direction, 

 is composed of a conglomerate converted into the hardest chert. In 

 many of the islands in the China Sea off Pahang the metamorphosed 

 rocks are so indistinguishable from greenstone, that we can only recog- 

 nise them as sedimentary by the presence of pebbles which some of 

 them contain. In Pulo Tioman the junction of granite with a green, 

 grey, and black hornblendic rock is well displayed, the granite sending 

 veins into the hornblende, and masses of the latter being sometimes 

 imbedded in the former, clearly proving that the hornblende, whether 

 volcanic or (as I believe) metamorphic, is the more ancient rock. 



* I trust to be able ere long to give a full account of the mechanical effects of 

 the upheaval in different parts of the district. 



f But common to it with the adjacent belts rising from the same platform — 

 that of S.E, Asia — and the approximately parallel and probably contemporaneous 

 Peninsula of Southern India. This peculiarity is found in S. India, Bengal, the 

 Malayan belt as far north as it has been examined, Borneo, and the N.W. part of 

 Australia. 



