glacial volume, all other things being equal, is associate! 

 witli a decrease in glacial velocity, and that the latter 

 is associated with a geometrical decrease in corrasive 

 strength, geologists should have perceived the fallacy 

 of attempting an explanation of recent glacial motion 

 along channels which have been formed by earlier and 

 mucli more powerful ice masses. The whole question 

 presents such a peculiar psychological problem, one so 

 insidious, that it will be well, at this stage, to call attention 

 to the various stumbling blocks in the way to the general 

 acceptance of the conception of recent powerful corrasion 

 by glaciers. In this way the younger generation of geolo- 

 gists may avoid the dynamical errors into which the fathers 

 of the science fell half a century ago, and into which indeed 

 some even of the present day leaders of the science have 

 fallen, their judgment being suspended as a result of the 

 influence of thei 



When Ramsay announced his hypothesis of the formation 

 of Alpine lake basins by glacial action, the geological world 

 quickly divided itself into two camps, namely, those who 

 believed, and those who did not believe, his doctrine. 

 Those who believed had the evidence that certain peculiar 

 and imposing land profiles were always and only found in 

 regions of recent glaciation. Moreover they had the 

 evidence that glaciers were capable of scratching, grooving 

 and plucking (quarrying) rock masses over which they had 

 passed. The unbelievers admitted the scratching and 

 polishing action of ice ; they admitted the removal of the 

 waste sheet, and the formation of roches moutonnees and of 

 some tarns by such action, but they saw nothing unusual 

 in the land profiles around them, nothing to suggest any- 

 thing but a slight or negligible modification of ordinary 

 stream channel profiles. To them the profiles of deglaciated 

 valleys were the "normal" types and such as could be 



