﻿1851.] 



LOGAN — GEOLOGY OF SINGAPORE. 



315 



the S,W. coast of Singapore, stretching from Sunge Pandan to Batu 

 Blyer (where the highest sea-cliffs in the district occur), and con- 

 tinued in the island of Blakang Mati. Proceeding along the same 

 line of elevation to the S.E., we find it again in P. Sikukur, the two 

 Sikijangs and Subar. It reappears on the other side of the Strait, and 

 on the same line, in the two Sambos (where we find sandstone, grit, 

 and conglomerate, for the most part highly indurated and semi- 

 crystalline ; clay, chocolate, light purplish, violet, greenish, and yel- 

 low ; and iron-rock), P. Miriam and the eastern portion of the N.W. 

 point of Batam. 



To the east of this line the chocolate and violet clays, which have 

 hitherto either shown themselves as isolated beds or in narrow bands 

 amongst the other strata, become continuous, occupying a breadth of 

 about one mile and stretching right across Singapore in the direction 

 of N.W. by W. This band includes P. Brani and the eastern por- 

 tion of Blakang Mati, in both of which the colours vary much, — 

 chocolate, purplish, different tints of violet, greyish, lilac, green, and 

 in which sandstone-layers are intercalated. It is then lost for about 

 six miles in the Strait, but is found again on the east side of Sambo 

 Kichi and on the coast of Batam, at Pulo and Tanjong Dangas. 



2nd zone. — The second zone consists almost wholly of soft amor- 

 phous clay and sandstone with conglomerate § the latter, however, 

 containing a good deal of clay either mixed with it or in separate 

 beds. The clay in Singapore forms a compact tract of about sixty 

 square miles, occupying the main body of the island*. On the south 

 it is separated from the plain of Singapore by a narrow margin of 

 sandstone, and then stretches across the island in a N. by E. direc- 

 tion to the Old Strait. On the west its boundary runs in a north- 

 westerly line, nearly parallel to the chocolate clay band, for about eight 

 miles, when it is deflected towards the N. in the direction of S. Kranji, 

 in the vicinity of which it meets the Old Strait. In Bukit Timah, 

 solid greenish granite and syenite, passing in some places into com- 

 pact laminated felspar, are seen. On some of the other hills of the 

 clay-tract, protruding blocks of syenite and granite are occasionally 

 found. Where deep sections have been made through the clay, its 

 structure and composition are found precisely to resemble that of 

 adjacent blocks, while on the surface it has a remarkable uniformity 

 of character f, and is easily distinguished from the sedimentary clays. 

 The whole of this tract, therefore, is decomposed plutonic rock. The 

 clay in some places, and particularly in the bottoms of valleys, where 

 it is covered by vegetable mud and has undergone a natural bleaching, 

 is a pure white kaolin, but it generally imbeds quartz-granules (in 

 rare cases abundantly), and a few feet below the surface is mottled 



* It is almost a square of eight miles, coinciding with the Peninsular axis ; that 

 is, two of its sides run N.W. by W. (the northern of the two giving its direction 

 to the Old Strait from T. Pongal to S. Tambrau), and the other two sides running 

 N.E. by N. (the northern of the two giving its direction to the Old Strait from 

 S. Sinoko to the creek of S. Batang Hari, and the southern giving its direction to 

 the ancient W. coast of Singapore Bay). 



f The variable proportions of iron and quartz, however, affect this character. 



