CHAPTER VIII. 



WHAT BECOMES OF THE " DUST " TOWNS AND CITIES. 



What becomes of Nature's " Dust "Its Amount The Visible Part Sand- 

 banks and Sand-dunes, River Sands Sandy Deserts Sand as a Pre- 

 server Uses of Sand Glass-making Sandstones and Precious Stones 

 Mud, Shales, and Slates A Great Mud-heap Effect of Pressure- 

 Porcelain Clays and Brick Clays A Mass of Sapphires and Rubies 

 Towns and Cities. 



IN countries where there are no violent earthquakes or 

 volcanoes, no tropical storms, and no glaciers, Nature's 

 labourers make and carry away their " dust," for the most 

 part, so quietly, and the hills look so very much the same 

 from year to year, and even from generation to generation, 

 that we may find some difficulty in realising that anything 

 at all is going on. Yet we are told that, by one means and 

 another, a mile in thickness has been worn away from the 

 Mendip Hills ; that the part of Kent and Sussex called the 

 Wealden has been stripped of a mass some hundreds of 

 square miles in extent, and several hundred yards in thick- 

 ness ; and that the district to the south of Snowdon has 

 lost from its surface a mass of 20,000 feet, a whole moun- 

 tain, in fact, as lofty as the Andes. 



Not an atom of all these many million tons of rock has 

 been lost, however, though it may have changed its appear- 

 ance so much as to be often hardly recognisable, and it is 

 when we consider what has become of it that we perhaps 



