STBEAM TIN DEPOSITS OF PEEAK, 223 



range has been rounded and moulded in a manner similar to all 

 mountain ranges of its class on the earth's surface. The crest of 

 the range rises and falls according to the projections of the rOcks 

 which are mostly bare on the summit, Weathering soon decom- 

 poses and rounds them, and the materials are swept to lower levels. 

 From the crest buttresses descend ; the drainage from which soon 

 carves out deep valleys on the sides. On these latteral buttresses 

 other valleys are cut down, and soon almost infinitely. The whole 

 thing, however complex, represents one huge system o£ drainage. 

 The great surface presented by the side of the range acts as an exten- 

 sive condenser to the moist air from the sea The water is ever rush- 

 ing down back to the ocean, first in rivulets, then in torrents, and 

 often, as an obstinate face of rock stops the water dashing over, in 

 angry cascades. It is never at rest. Each day the process of wear- 

 ing away goes on in thousands of rills and streams. But observe 

 that it is not water alone which is doing the work. The sand and 

 fragments of rock carried down by the water does the great work of 

 scouring and cutting down the valleys, and the mountains are thus 

 very slowly but surely worn away. 



At one time in their history, probably these mountains were 

 upheaved, but upheaval has little to do with their present form. 

 The features which so many mountains share in common, point to 

 some common cause for all, and this is what we call weathering, 

 erosion or denudation. It is the effect of the friction of water and 

 sand just as we see in the case of the water- worn pebble. So when 

 you hold that pebble in your hand, you hold in miniature what the 

 water is doing in the hills around you. Water is the universal 

 solvent, and the law of gravity does the rest. Hocks are under- 

 mined and come tumbling down in landslips which fill up the 

 valleys. Water pounces upon them here again and gives the stones 

 no rest. They are worn away and carried to the sea, and the val- 

 ley is scooped out again waiting for other supplies of material. 

 Thus, gradually, main ridges become scarped and cut dow r n by side 

 valleys until they dwindle away. The materials are carried into 

 plains which gradually build up islands and mud flats such as those 

 which front the western side of the Malay Peninsula. 



Those who have visited the top of the range must have re- 

 marked how the crystals of felspar stand out from the surface 

 of the granite just like pebbles in conglomerate. They often pro- 

 ject an inch or more. Weathering has dissolved away the rock 

 around them. Their crystalline structure and compact form enable 

 them to resist decomposition, and thus they remain, for a time, as a 



