1196 GEOLOGY AND PHYSICAL GEOGRAPHY OF THE STATE OF PERAK, 



reason for this. The water is quite colourless in small quantities. 

 I am inclined to think it is due to a hydrated silicate of alumina 

 (Halloysite) derived from the clays, but it may be also a minute 

 diatom (Tryblionella 1) which is sparingly found in the water. 

 See Note. 



The tin in all these mines is abundant, rather coarse, and often 

 in two strata of a foot or more in thickness. It is generally in 

 the lowest portion of the drift, covered with coarse water-worn 

 sands and gravel, fine yellow and white sands and vegetable 

 matter in regular sti"ata. 



Salak. 



This mine is situated in a valley formed by granitic spurs from 

 the range on the eastern side of the Perak River. It is about four 

 miles east of Enggor, a village on the river about five miles north 

 of Kuala Kangsa. The workings are in a small river valley which 

 at the time of my visit (February 6th, 1884) was nearly dry. All 

 the workings were in alluvial drift with coarse gravel , but with much 

 fine sand above. In the bed of the river there were outcrops of 

 very hard stratified quartzite forming bars aci'oss the stream. 

 These have acted as " ripples " and consequently much drift tin 

 was accumulated on the upper sides of them. I was told that 

 there were indications of a tin vein here but I saw none. The 

 whole of this valley must be rich in tin, but it is only worked to a 

 small extent as yet, by Chinese. The tin is excellent, with grains 

 of a large size. I saw some crystals half an inch in diameter with 

 little signs of abrasion. 



Note. — The action of water holding carbonic acid in solution (derived 

 from the vegetation) accounts for most of the changes in the clays and 

 sands of these localities. The orthoclase felspar containing potash becomes 

 easily soluble in carbonized waters. Thus the potash becomes carbonate 

 of potash and the silica of the felspar is set free, partly in solution, and 

 partly as siliceous sand. Nearly all the water in these pools gives a 

 slightly alkaline reaction. I need hardly say that carbonate of potash is a 

 very soluble salt and easily carried away by running water. Soda felspars 

 are not so common in the granite here, but if present a similar process of 

 solution goes on, only that the product is carbonate of soda. 



