294 GLACIAL GEAVELS OF MAINE. 



precipitation here near the sea mnst have been larg'e, even if diminished 

 from what it had been during the time of maximum glaciation. 



For these and other reasons we postulate a larger water discharge in 

 Maine in late glacial times than the present. The glacial rivers exceeded 

 the present rivers in number and had correspondingly smaller drainage 

 basins. This tended to diminish the size of the individual rivers, yet some 

 of them have left level plains one-eighth to one-half mile wide, and appear 

 to have equaled or surpassed the discharge of the larger rivers of the present 

 time. 



ZONES OF THE MAINE ICE-SHEET. 



According to the accounts of the explorers named above, the interior 

 of Greenland is covered with snow fields. At the highest elevations if there 

 is any melting it is limited, since Nordenskjold's Laps found the surface dry 

 and powdery. At lower elevations the melting becomes more abundant 

 and the surface waters slowly ooze through a zone of slush. Then we find 

 pits filled with water, and, by degrees, the waters uniting to form surface 

 streams. Some of these have been traced for several miles and are from 

 4 t© 10 feet wide. Still descending, we find crevasses appearing, sometimes 

 near the nunataks, at other times where none are visible but where the ice 

 is probably flowing over a buried ridge. Into the crevasses the surface 

 streams pour and disappear, escaping as subglacial or englacial streams. 

 Sometimes they pour with a loud roar into small lakes within the ice. 

 Some of the crevasses are very wide as well as deep, one observed by 

 -Lieutenant Peary being 50 feet Avide. As we approach the outer margin 

 the surface becomes indescribably rough with blocks, hummocks, and ridges. 

 Here the water derived from surface melting need flow only a few feet or 

 rods befoxe plunging into the depths. 



These observations give us a general conception of an ice-sheet with 

 respect to its waters of surface melting. Over all the region broken by 

 crevasses we have an elaborate system of subglacial and englacial streams 

 which receive the waters of the short surface streamlets. Above this zone 

 is another, of superficial streams, then the area where the snow absorbs all 

 the water of surface melting, which becomes progressively less as we go 

 upward. 



Applying these principles to Maine, we note that the average slope of 

 the land southward is only from 3 to 10 feet per mile, much less than is 



