14 SOILS 



sands of hills and mountains is large. Here we see a 

 mighty force and a powerful agent at work in soil making. 



The sorting power of water. In this connection we 

 should not forget the work of water as it moves silt, clay, 

 pebbles, and stone that have been caught in its channels 

 and then moved downward toward its emptyings. Silt 

 and clay are readily held in suspension even if the water 

 is slow going. It requires rapid currents to move the 

 heavier, coarser stones and pebbles. As these are carried 

 along, their rough edges are worn off, their sides are 

 scraped and scratched, and many particles are pulverized 

 and ground all contributing to soil making. TO be sure, 

 this soil will be deposited in lower regions, yet it is now 

 soil, the same as that in the cultivated field or garden. 



The role that ice has played. In the northern part of 

 the United States we have a class of soils formed by giant 

 masses of ice called glaciers, that moved in a southward 

 course many, many centuries ago. Our ideas of the cause 

 of this vast body of moving ice are not clear and we have 

 only the evidence that once it was so. We are told that all 

 the northern part of our country was covered with a 

 frozen mass of ice and snow, and that for some reason this 

 whole mass assumed a moving character, creeping over 

 plain and stream, attacking every hill top and mountain 

 range, and without further ado, conquering them as if 

 play mounds made by children's hands were the confront- 

 ing power. 



As this huge mass moved onward in its course it 

 gathered up huge rocks that once were free, quarried 

 other giants from the bosoms of the mountains, and 

 played with them as it went along rolling them, forcing 

 them together, dragging them, rubbing their rough faces 

 until they were smooth (if perchance they were not com- 

 pletely ground into powder) until finally the rays of the 



