98 Kansas Academy of Science. 



posits laid down by glacial streams in the open valley just 

 beyond the ice front. These sediments spread out and filled 

 the valleys not unlike the sediments of Alpine glaciers do to- 

 day. They left a rolling, uneven surface, with shallow hol- 

 lows, but no deep kettle-holes or conspicuous reticulations. 

 They are often distributed along the moraines for a great 

 distance and constitute a fringe of assorted material to which 

 Shaler has given the apt name "apron." The material varies 

 widely in coarseness, according to the condition of the forma- 

 tion. Classified structurally, they are known as gravel, sand, 

 and silt aprons. 



OUTWASH Apron Deposits. — These are tracts of assorted 

 material formed by waters outflowing from the ice where no 

 definite terminal ridging took place. This class is usually 

 made up of sand. 



PITTED PLAINS. 



Both the osar deltas and the overwash aprons are charac- 

 terized in certain regions by a surface marked with numerous 

 depressions, sometimes symmetrical (kettles) , sometimes ir- 

 regular, with undulating bottoms and embracing knolls and 

 subbasins, which give the surface an expression resembling 

 kames. A part of these pitted plains seem to be intimately 

 connected in origin with the ice edge and to be due to marginal 

 conditions, of which it has been thought that the incorporation 

 of ice fragments, the grounding of ice blocks, the movement 

 of the ice edge, and the development of underground ice- 

 sheets were among the special agencies. 



Osar Pit. — Another class of pits was found at the ter- 

 minus of osars. They are probably due to the water's scoop- 

 ing out a hole at the point where the osar waters emerged 

 from the ice. In many cases these holes are now swamps. 



EXTRAGLACIAL DEPOSITS. 



These deposits are of glacial origin. They, however, were 

 laid down either by wind or water beyond the ice-foot. They 

 are: 



Glacial River Deposits. — These were laid down by the 

 ice-streams as they issued from the body of the active glacier. 



Valley Drift. — As the glacial streams were greatly over- 

 loaded with debris at their outlet they built up their valley 

 bottoms by depositing material from bluff to bluff, forming a 

 valley plain. Out of this, beautiful systems of terraces were 



