40 



which then rises above the banks, overflowing the surrounding 

 country. Then, since its current is checked where it is so shallow, 

 the water drops some of its load of rock bits on the flood-plain, 

 much as the muddy water in a gutter drops sand or mud on the 

 sidewalk when, in time of heavy rains, it overflows the sidewalk. 



Many of the most fertile lands of the world are flood-plains of this 

 kind, where sediment, gathered by the streams farther up their 

 courses, is dropped upon the flood-plains, enriching them by new layer.'' 



17. — Near meic of a cut in glacial soil, gullied by the rains, and toith numer- 

 ous transported pebbles embedded in the rock flour. 



of fertile soil. One does not need to go to the Nile, the Yellow or the 

 Mississippi for illustrations of this ; they abound on every hand and 

 many thousands of illustrations, great and small, may be found in 

 the State of New York. Doubtless you can And one. 



There are other ways in which soils may be formed (Fig. 17)5 

 but only one more will be considered, and that is the way in which 

 most of the soils of New York have been made. To study tliis 

 let us go to a cut in the earth, such as a well or a stream bank (Figs. 

 15 and 17). Scattered through the soil numerous pebbles and 



433 



