THE GREAT PLAINS 403 



and, as a rule, rich harvests could be obtained. The soil 

 here is transported soil ; it is deep and unlike that of the 

 underlying rock. In some places it is rather stony and in 

 others very fine and without stones. It is so deep that the 

 underlying rock is only seen in deep cuts. 



This soil was probably deposited by the great conti- 

 nental glaciers which once covered the region and was 



ALFALFA CUTTING ON THE FERTILE PRAIRIES. 



spread out either by the action of the slowly moving ice 

 or by the water from the melting ice. This water flowed 

 over the surface in shallow debris-laden streams, bearing 

 their silt into the still waters of transient ice-dammed 

 lakeSc Whatever the original surface of the region, at 

 present it is an irregularly filled plain due to the ancient 

 ice sheet. As the soil is composed of pulverized rock not 

 previously exhausted by vegetable growth it is strong and 

 enduring, so that this country has, since its settlement, 

 been noted for its productivity. 



187. The Great Plains of the United States. West of the 

 Mississippi River, and merging almost imperceptibly into 

 the prairie region on the north and the coastal plain region 

 on the south, there is a broad extent of territory usually 



