SUBGLACIAL AND ENGLACIAL STREAMS. 297 



higher the englacial debris rose in the ice the more would the superficial 

 and englacial streams be able to collect. Those who believe the englacial 

 matter to have been strictly basal will not admit that either class of streams 

 would be able to gather much sediment until their beds sank nearly to the 

 ground. 



Second, the englacial channels were often simple conduits for streams 

 otherwise subglacial. As such, their mission may have been simply to 

 protect the ground moraine from erosion, or glacial gravels may have been 

 deposited in them. In the last case the stratification of the sediments 

 would be generally obliterated by the melting of the subjacent ice. 



In Maine I have discovered numerous places in the line of long glacial 

 rivers where the ground moraine is less eroded than in the case of some of 

 the short hillside eskers, as, for instance, at The Notch, in Garland. Both 

 to the north and south the stratification, etc., are consistent with the 

 hypothesis that these were subglaicial rivers through most of their course. 

 How can we account for so little erosion of the ground moraine 1 At one 

 time I considered these places strong evidence that the osar rivers were 

 superficial as a whole, but it must now be admitted that they may imply 

 only an englacial or superficial course of a subglacial river for a short 

 portion of its length. Thus in the jaws of the naiTOw pass of The Notch, 

 Garland, the basal ice may have been so solid that for a mile or more a 

 subglacial river was forced to rise into or on the ice. In 1888 I suggested 

 that such accidents might not be uncommon, but without observational 

 basis for the idea. Without insisting on close aiialogies between the 

 Alaskan glaciers and the ice-sheet, we must at least consider englacial 

 streams as one of the forms of a glacial water action-, and probably an 

 important one. 



DIRECTIONS OF SUBGLACIAL AND ENGLACIAL STREAMS UNDER EXISTING 



GLACIERS. 



The recorded observations bearing on this subject are too few to 

 permit generalization. The courses of only a few of the subglacial rivers 

 are more than approximately known. At the terminal enlargement of 

 the glacier of the Rlione, the courses of the subglacial streams have 

 been mapped, and it is known that some of them flow transversely to the 

 direction of ice flow. But this takes place longitudinally and where the^ 



