﻿196 



THE SECONDARY STANNIFEROUS DEPOSITS [vol. lxxii,. 



planes, while the general character and disposition of the pre- 

 granite deposits did not support the supposition of extensive 

 faulting. The occurrence of tinstone on each side of the valley, 

 hut not in the middle of it, indicated its genetic connexion solejy 

 with the bordering intrusive granite. The peculiar weathering 

 of rocks in the wet regions of the tropics was remarkable. In 

 railway- and road-sections in the Gold Coast Colony he had seen 

 thick masses of decomposed biotite-gneiss, of thin phyllites and 

 altered sandstones, and of altered sandy mudstones which had 

 changed into sandy clays, so similar as to be indistinguishable 

 one from the other. The lamination of the rocks in large portions 

 had disappeared entirely, and all of them might easily be mistaken 

 in many places for cla} r s of a late period. 



Dr. Herbert H. Tho^ias regretted the absence of Mr. Scrivener, 

 but thought that the Author had presented to the Society mature 

 conclusion based on careful observation. It was important to 

 bear in mind that, when the Author commenced work in the 

 Malay States, he was evidently inclined to regard the glacial 

 origin as the only possible explanation of the peculiarities of the 

 Gropeng Beds ; but, as his work progressed, he came to regard the 

 previously-accepted view as untenable. The speaker hoped that 

 the Society would publish the paper, in order that it might be 

 more fully discussed than was possible at the moment. 



The Author, in the course of his reply, said that the study of 

 British rocks by anyone familiar with weathering in a moist 

 tropical climate would, as Prof. Watts suggested, be a useful piece 

 of investigation, especially with respect to beds deposited during the 

 prevalence of a tropical or subtropical climate. Prof. Fearnsides 

 nad raised the cmestion of kaolinization, which was full of 

 interest to him, for he had been fortunate in seeing the chief 

 kaolin - deposits of China, some of those of Japan, and he had 

 described elsewhere 1 those of the Federated Malay States. Kaolini- 

 zation seemed to be the result of atmospheric weathering near 

 Kingtehchen in China, and of both atmospheric weathering and 

 pneumatolysis in Malaya. The kaolin resulting from the former 

 cause was found, in several tests, to be less soluble in dilute 

 sulphuric acid than similarly-treated kaolin from veins where 

 pneumatolytic agents had obviously played an important part. 

 He hoped to publish shortly the results of his observations on 

 kaolinization, observations carried out in exceptionally favourable 

 circumstances. 



In answer to a question on the absence of a glaciated floor 

 in the limestone underlying the clays of the Kinta Valley, it was 

 necessary to point out that, although in India (near the village of 

 Irai, along the banks of the Pern near its confluence with the 

 Wardha) the Kadapah Limestone underlying the Talchir glacial 

 clays is described as being deeply grooved, it should be remembered 

 that the percolating water in the Kinta Valley, after flowing over 



1 W. E. Jones, ' Clays of Economic Importance in the Federated Malay- 

 States ' Government Printing Office, Kuala Lumpur, 1915. 



