1184 GEOLOGY AND PHYSICAL GEOGRAPHY OF THE STATE OF PERAK, 



drift. This is composed of clays, fine sand, fine or coarse gravel 

 which is large near the hills, and finally tin sand, which rests upon 

 blue, white or red clays. The sand is quartzose, angular, composed 

 of transported grains, evidently sifted by water and not abraded. 

 It is transparent, showing much color under the polariscope. The 

 pebbles in the gravel are rounded granite, with black mica, schorl, 

 and grains of tin. 



There ax-e also rounded fragments of quartz of various colours, 

 generally opaque white, but also red, brown, i-ose coloured, and 

 violet. The two latter tints are due to fluor spar. The whole of 

 the deposits have been derived from the granite and the tin has 

 sunk to the lowest level by the force of gravitation. The drifts are 

 sometimes full of stumps of trees and large stems of fallen timber. 

 There ai'e also the reuiains of jungle swamps which have given rise 

 to deposits of black and brown humus full of roots, stumps, trees, 

 leaves, &c. This deposit loses half its weight on drying, and the 

 remainder burns leaving half its weight of ash. Remains of boats, 

 paddles and fragments of pottery have occasionally been found in 

 the drift. Except when covered with vegetable remains it is of a 

 light colour and gives rise to a poor soil, covered with Calang 

 (Imperata arundinacea) or jungle. 



3. Paleozoic Clays. — These generally form the bottom on which 

 the tin sand rests. They ai-e much decomposed, yet preserve the 

 marks of former sti-atification. They have been contorted and 

 metamorphosed, sometimes resembling Gneiss. There are cross 

 veins of white quartz and felspar in certain portions, showing 

 metamorphism. Brick red and yellow sandstone bands are 

 frequently intercalated. The common result of decomposition on 

 this rock caused by water containing carbonic acid is to change it 

 into red brick earth, which goes by the name of " Laterite." The 

 use of this term throughout the peninsula is inconvenient and 

 should be discontinued because it groups under one name several 

 formations. Any rocks, such as trap, granite, and gneiss, may 

 decompose into a red earth through the influence of water strain- 

 ing through vegetable matter and containing carbonic acid. A 

 very small quantity of iron being thus converted into peroxide 



