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PROCEEDINGS OF THE GEOLOGICAL SOCIETY. [June 25, 



at Tanjong Lompatan, talcose shale, quartz, and iron-rock ; — along 

 the north coast of Bintang, from Tanjong Subong to the N.E. Point, 

 syenite* ; at the Point, talcose clay and shale with iron-rock f, and 

 quartz (similar to T. Kmawar) J. 



3. Character and Extent of each kind of Rock. 



1 . The Sedimentary Rocks. — Viewing the district as a whole, we 

 observe that amongst the sedimentary rocks the shales greatly pre- 

 dominate, the chocolate and purplish being the most common. The 

 soft shales and clays are of far greater extent than the indurated, and 

 are either quite soft, yielding to the hand, or have various degrees of 

 consistency, up to so much hardness and toughness as to require the 

 hammer to break them. They are in great measure a mixture of 

 clay and fine siliceous granules, to which the term marl may be ap- 

 plied, but as descriptive of their consistency only, for none of them 

 are calcareous. Those in which clay is in excess, so as to be com- 

 pletely plastic, are not frequent. The steatite, when it occurs, is 

 generally in large proportion, but of limited extent. I have only 

 observed completely indurated argillaceous and argillo-siliceous rocks 

 of a cherty and jaspery nature, and considerable in extent, at Pulo 

 Salu, P. Kapal, P. Piel Ayem, Tanjong Putri (western), Pulo Sijahat, 

 Pulo Ilantu III, and Tanjong Pingrang §. 



The sandstones and conglomerates are more often indurated than 

 friable. In many cases the former have a subcrystalline texture, and 

 the latter a compact siliceous basis, traversed by veins of quartz- 

 crystals. The most numerous pebbles in the conglomerates are of a 

 dull whitish quartz. Greyish quartz-pebbles are also common. Black, 

 red, and yellowish pebbles occur sparingly, although in some locali- 

 ties more abundantly than in others. Felspathic pebbles, sometimes 

 with a crystalline, but generally with an earthy fracture, are common, 

 violet tints prevailing. The basis of the conglomerates, when not in- 

 durated, varies from clay, often chloritic or steatitic, to a friable earth 

 or marl, sometimes also chloritic, containing an abundance of quartz- 

 granules. The highly indurated and subcrystalline sandstones chiefly 

 occur m Mount Palmer (24), Government Hill (34), Mount Sophia 

 (48), and Mount Liligi in Singapore, and in the promontory termi- 

 nating at Tanjong Singwang in Batam. 



2. The Plutonic Rocks. — Taking a similar broad view of the pluto- 



* J. T. Thomson, Esq. 



f Mr. Thomson says, that " Laterite in a fused state appears to have run into 

 and over this stratum in several places so as to crack it." 



The lava-like appearance of the hydrous peroxide of iron here and in numerous 

 other localities is exceedingly deceptive. I was misled hy it for a considerable 

 period, and the views which I have communicated to the Asiatic Society respect- 

 ing the geology of this region were more or less coloured by this notion. The 

 ejected-fluid-aspect and blackish colours are entirely owing to the peroxidation 

 and concreting process of the iron. Is not the iron-dyke in Mavrospilia, which 

 puzzled M. Virlet d'Aoust (Expedition Scientifique de Moree, pp. 54, 55), capable 

 of a similar explanation ? 



t Specimens from J. T. Thomson, Esq. 



§ P. Pisang (N.W. of P. Kocob, beyond the limits of the map) and the east 

 coast of Krimun Kichi are striking examples of this class of rocks. 



