upper over the lower layers or by the almost intinitely slow 

 rotation of large ice granules one upon the other?" The 

 obvious answer to all these questions was first :— that all 

 glaciers to day are passing through a decadent phase, that 

 large as the Greenland, Spitsbergen, and Antarctic glaciers 

 are as compared with those of the Alps or of temperate 

 regions generally, nevertheless they are but the enfeebled 

 representatives of recent Ice Floods ; second, that the 

 tortuous markings found along the floors and walls of the 

 deglaciated valley portions 1 evidence the greater plasticity 

 of the recent glaciers, and that therefore these departed 

 Ice Floods must have possessed a mobility inconceivable 

 from a mere study of present day glaciers. 



There are several ways of arriving at this conclusion if 

 one believes that glaciers are gravity streams ; that the 

 present glaciers are capable of erosion in even a slight 

 degree, and that the recent Ice Floods lasted for some 

 thousand of years. [All this, as one knows, is conceded by 

 all geologists]. One could approach the subject from the 

 standpoint of plasticity itself. For if the Ice Flood did 

 excavate a channel adjusted to its needs, then any marked 

 diminution in glacial volume would be accompanied by a 

 great decrease in pressure, and a decided return thereby 

 to a crystalline solid condition on the part of the glacier at 

 the points where the greatest interruptions of channel base 

 occur, with a corresponding sluggishness and alteration of 

 form for the textural units of the glacier. 



Or again, one could approach the subject from a con- 

 sideration of the work accomplished by a glacier, the term 

 work being used in its dynamical sense. Thus for a glacier 

 to be enabled to eon-ad-- a point of its eliannel base it must, 

 in common with any other gravity stream, carry its load 



1 Andrews, E. (.'., <J P . tit., pp. 264-268. 



