52 SOILS: PROPERTIES AND MANAGEMENT 



narrow band of material to collect by the continual 

 melting of the ice and a consequent dumping of its load 

 of debris. This moraine is by no means continuous, 

 and for miles across the continent no trace of it can be 

 found. It extends, roughly, eastward from the Canadian 

 border in Washington to the upper sources of the Missouri 

 River, then down that river to St. Louis, up the Ohio 

 River, northeastward until the southwest border of 

 New York is reached, and then southeast to New York 

 City and Long Island. Many other moraines are found 

 to the northward, marking points where the ice became 

 stationary for a time during its retreat. 



38. The ice as a soil builder. — It was during these 

 retreats that the ice acted as a soil-forming agent. Ma- 

 terial gathered and ground by the ice as it pushed to the 

 southward was finely pulverized and it is only natural 

 to suppose that this debris was deposited as the ice slowly 

 retreated by the melting back of its margins. The 

 material laid down as a great mantle over the glaciated 

 areas is called drift. Some of this has been reworked 

 and stratified by water, but a very large proportion has 

 remained untouched since it was laid down by the melt- 

 ing ice. It presents in most cases — except at the very 

 surface, where weathering may have occurred or organic 

 matter accumulated — exactly the same condition as 

 when deposited. This mass of un stratified material is 

 heterogeneous, both as to size of the particles that make 

 it up and as to its rock composition. It may be coarse 

 and bowldery, especially in mountains or where there 

 are gneisses or schists, or it may be very fine where the 

 rocks are soft. Bowlder clay is a term sometimes used 

 in describing the matrix of this glacial deposit. In some 

 cases foliation occurs, and often coarse and fine layers 



