Federated Malay States. 461 



The rock at 101st mile differs in that it is fine-grained; it 

 contains interstitial quartz, and all the augite has been, altered to 

 a chloritic mineral. It contains a good deal of calcite, possibly 

 derived from the decomposition of the felspars, which enclose 

 numerous white mica flakes, and it also contains abundant ilmenite. 



There are a number of dolerites known in the Peninsula which are 

 of a considerably later period of eruption. In some cases the 

 intrusion occurs in quartzite, and is therefore probably of later age 

 than the Uondwana Series, in other cases still the dolerite dykes 

 penetrate the Mesozoic granite, and the latter, like many acid intrusive 

 rocks which penetrate the granite, are not included in the Pahang 

 Volcanic Series. 



There are other intrusions of doubtful age where the field evidence 

 is not sufficient to assign them definitely to one of the two groups. 

 The dolerite of Batu Bersawah* gold-mine in Negri Sembilan, which 

 is intrusive into Raub shales and limestones, is veined with calcite 

 and has been much sheared, so there is no doubt that it belongs to an 

 early period of eruption, for it is probable that the only extensive 

 shearing movements in this district took place at the time of the 

 intrusion of the Mesozoic granite. The rock is much weathered, the 

 ferromagnesian mineral being completely altered, and chlorite, 

 pyrite, and ilmenite partly changed to leucoxene are abundant. 



A rock with ophitie structure occurs in two localities along the 

 road * from Kuala Lumpur to Bentong as a band about two yards 

 wide in phyllites at the 17^ mile, and in a high cutting 250 yards 

 short of the 21st mile as a band in contact with sheared chert and 

 within a few yards of a large devolopment of felspathic grits. It 

 was seen by Mr. Scrivenor in 1907 as lenses between chert bands 

 exposed in the road-cuttings which were newly made at that time, 

 suggesting that the rock is a pillow-lava. Mr. Scrivenor collected 

 chert specimens from near the 17th mile also in 1907, but weathering 

 has since destroyed the freshness of the exposures. 



The rock at the 17^ mile is dark-grey and finely crystalline, 

 made up of good-shaped narrow prisms of felspar about J mm. long, 

 with a low extinction angle corresponding to oligoclase, and poorly 

 shaped crystals of hornblende of the same size. There is nearly as 

 much hornblende as there is felspar, and it is noteworthy that the 

 felspars have a better crystal shape than the hornblende. Occasionally 

 there is a larger and broader phenocryst of oligoclase with length of 

 nearly 2 mm. There is a little apatite and a little quartz as 

 interstitial grains. Abundant cubes and grains of pyrites are 

 disseminated throughout the rock, probably all of it secondary, and 

 veins and streaks made up of fibrous serpentine or chlorite, quartz, 

 and an opaque fine-grained dust also make up a considerable pro- 

 portion of the rock. 



Many specimens of the rock near the 21st mile have been 

 examined, very similar in texture and colour to the above in the 

 hand-specimen. Felspar prisms, like those described above, make 

 up the same proportion of the rock, but there is a total absence of 

 hornblende, the spaces intervening between felspar prisms being 

 filled with serpentine or chlorite, quartz, ilmenite skeletons, and 

 calcite. There are no porphyritic felspars and no apatite was 



