130 LIFE ON THE EARTH. 



which threaten to fall, and must soon be removed ; 

 see this, which is a fair specimen of the average waste 

 of English coasts, and specially of the south coast, 

 before adopting an estimate of the rate of annual 

 loss. In his recent work, On the Origin of Species, 

 Mr Darwin assumes the rate of waste for the Weal- 

 den coast to be one inch in a century; I should 

 have preferred, and do prefer, an estimate of one 

 inch in a year, that is to say, one hundred times as 

 great, and I suppose that by most observers this 

 will be thought too low an estimate for all but the 

 most invincible coasts. Still the effect of all this 

 violence of the waves on the production of materials 

 for the sea to deposit in new strata is not great, 

 compared to the powerful action of the atmosphere 

 on the broad surfaces of the land. 



For example, assume an extravagantly high rate 

 of waste, such as that on the coasts of England, 

 which certainly cannot equal 1 foot in a year ; apply 

 it to the whole of the sea-coasts of the world ; assume 

 these to be equal to four circuits of the globe, that 

 is to say, 100,000 miles in extent, and 100 feet high. 



.,, , 100000 x 100 x 1 

 The annual waste will be - . - = 0*4 cubic 



miles of sediment. The area of the land being as 

 before assumed equal to the area of new deposits, 

 we have 50,000,000 sq. miles covered 2 oVoth inch 



