224 STREAM TIN DEPOSITS OP PERAK. 



record of what water has done, 



If, then, the Thaipeng Range has thus assumed its present form 

 by the action of water, we may assume that we have no means of 

 knowing the extent to which it has been worn away. It certainly 

 was higher than it is, and I shall show you what reason there is for 

 believing that it was covered by other formations. But one thing 

 we can certainly say. It has not been recently raised from the sea. 

 llecent marine remains are entirely absent from it. I need not 

 tell you perhaps that the sea never leaves doubtful signs of its pre- 

 sence where it has once been. Its infinite treasures of life leave 

 millions of relics behind to mark the history of its stay. Nothing of 

 the kind is seen here. Instead, we have layers of vegetable remains 

 to mark what has been the former land surface and how' it has 

 supported only plant life. 



To find out the geological history of these hills we must inter- 

 rogate the only record that remains to us, that is,, the mate- 

 rial derived from the rocks, the drifts, sands and mud banks. 

 This at first would not seem to be a very hopeful enquiry. But 

 more evidence will be forthcoming from it than one would think. 

 Daubree's experiments have shown that rocks are broke li smaller 

 and smaller by water until there comes a time when friction and 

 abrasion have no longer any power. This is when they are re- 

 duced to fragments about one-fiftieth of an inch in diameter. Not 

 only do they then cease to become broken, but the fragments do 

 not readily become rounded or abraded at the edges. Such frag- 

 ments are easily examined by microscopes of moderate power. By 

 its aid the sand tells us its history. If it be from the sea, particles 

 of lime and shell with other familiar remains soon tell its origin. 

 If it were aerial or from a desert, every particle will be rounded, 

 abraded and opaque. If from fresh water there will be carbona- 

 ceous matter and a peculiar sorting of the materials which I shall 

 explain more fully. 



With these facts as a guide, let us now examine the material 

 which has come down to the plains from the mountains. Close to 

 the hills we shall find boulders and heavy gravel. Their weight 

 obviously prevents these materials from travelling far. Amongst 

 the boulders, some are angular, or just as they have rolled down 

 from the hills, and some are rounded by water. Further out in the 

 plain, we find alluvium and certain outliers of rocks which have as 

 yet escaped denudation. These sometimes rise into detached hil- 

 locks, such as the Resident's Hill. Or they may scarcely rise above 

 the surface at all, such as the red clays near the Thaipeng gaol. 

 These clays are most important, and we shall consider them more 



