THE SOIL 3 



stream just after a washing rain. The clear waters are 

 uglied and discolored by mud washed in from the surround- 

 ing hills. As though disliking their muddy burden, the 

 waters strive to throw it off. Here, as low banks offer 

 chance, they run out into shallows and drop some of 

 it. Here, as they pass some quiet pool, they deposit 

 more. At last they reach the still water at the mouth, 



FlG. I. ROCK MARKED BY THE SCRAPING OF A 

 GLACIER OVER IT 



and there they shake off the last of their mud load, and 

 often form of it little islands, or deltas. In the same way, 

 bearing acres of soil in their waters, mighty rivers like 

 the Amazon, the Mississippi, and the Hudson, when they 

 are swollen by rain, sweep to the seas. Some soil they 

 scatter over the lowlands as they whirl seaward ; the rest 

 they deposit in deltas at their mouths. It is estimated 

 that the Mississippi carries to the ocean each year enough 



