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DR. W. R. JONES ON THE SECONDARY [vol. lxxii, 



collections of fossils in rocks far removed from Europe ' 1 ; that 

 they have been correlated with the Talchir Beds of India ; and 

 have been used as the horizon on which to base the geological 

 age of rocks that cover over a quarter of the surface of the Malay 

 Peninsula. 2 If they are of glacial origin and of the same age as 

 the Talchir rocks they should extend under the 'younger Gondvvana 

 rocks ' mapped by Mr. Scrivenor, and consequently other extensive 

 tin-fields would remain to be discovered in the Malay Peninsula. 



The object of the present paper is to show that all the tin-ore 

 found in the 'clays and boulder-clays' of the Kinta Valley has 

 been derived from rocks now in situ in the Kinta district ; that 

 it is unnecessary to bring in glacial agency to explain any of the 

 features which led Mr. Scrivenor to adopt that theory of their 

 origin ; to point out that these deposits cannot be considered of the 

 same age as the Talchir Beds of India ; and to show that a simple 

 interpretation may be given to the geological phenomena of the 

 Kinta district. 



Evidence will be advanced to show that these 1 clays and boulder- 

 clays ' are in some places alluvial deposits and in others the result 

 of weathering in situ of phyllites and schists, which have after- 

 wards either subsided on the dissolving metamorphosed limestone 

 that everywhere has been proved to underlie them, or slipped down 

 the valley sides. It will be shown that the richest tin-ore deposits 

 occur, without exception, near to granite or to granitic intrusions 

 proved to be cassiterite-bearing, and that the deposits farthest 

 from these igneous intrusions contain no tin-ore. All the features 

 which led to the adoption of the glacial theory of the origin of 

 these deposits will be shown to be the results of intense weathering 

 in a moist tropical climate, such as have been described in other 

 tropical countries. 



All the types of rock and mineral present in the supposed ' glacial 

 clays ' have been proved in situ in the older rocks of the district ; 

 and, in the case of the tin-ore, these sources will be shown to be 

 sufficient to account for all the ore in these clays. 



II. General Description oe the Kinta District. 



The Kinta District is in the centre of the State of Perak, 

 and is bounded on the east by that part of the watershed of the 

 Main Range which lies between Gunong Kerbau (7160 feet above 

 sea-level) on the north-east and Gunong Pergantong (4740 feet) 

 on the south-east. On the west the Kledang Range forms the 

 boundary, except between Siputeh and Tronoh where the range 

 disappears. The northern boundary is the rising ground north of 

 Chemor, and the southern boundary extends westwards from 



1 ' The Geological History of the Malay Peninsula ' Q. J. G-. S. vol. lxix 

 (1913) p. 353. 



2 Ibid. p. 370 & pi. sxxv. 



