THE SOIL MAKERS 15 



more southern sun robbed the glacier of its power by 

 melting snow and ice, which freed, rushed on into river 

 channels to be lost at last in the seas of the East and the 

 South. 



Soils that were formed by this moving mass of ice are 

 known as drift soils. Such soils vary greatly in composi- 

 tion and in physical nature. The area formed by these 

 glacier or drift soils is altogether lacking in uniformity, 

 its surface is broken often abrupt, its elevation is some- 

 times considerable, often but slight and its producing 

 power is modified by the nature of the deposits. \Yhile 

 it is true that these soils are fairly well supplied with 

 necessary mineral constituents essential to plant growth 



JUST AFTER A FLOOD 



they are often deficient in organic matter the source of 

 nitrogen supply. 



Wind made soils. While the wind is often most vigor- 

 ous in its activitv, it is a reasonablv slow agent in soil 

 making, when considered by its daily work : it must be 

 studied only in its aggregate in respect t<> all the geolog- 



