AMOUNT OF LAND WASTE IO3 



The total amount of material which has been removed from the 

 land surfaces by the atmospheric agencies and carried to the sea 

 by rivers is incalculably great. The Appalachian mountain system 

 has thus lost thicknesses of rock which vary in different regions 

 from 8000 to 20,000 feet, and it is altogether probable that the 

 average waste of all the continents amounts to several thousands 

 of feet. The figures given for the basins of the Mississippi and 

 the Ganges show that such wastes imply enormously long periods 

 of time. 



