RHYTHM 313 



related to the gouge length, being greater when the length is greater, but 

 there is no fixed ratio between the two. No measurements were made in 

 the field, but photographs show a range in the ratio from about 1 : 3 to 

 about 2:1. 



The discussion of the gouge rhythm also suggests the possibility that 

 the ordinary movement of the glacier on its bed may be rhythmic. It is 

 certainly conceivable that internal strains and stresses of the rock and ice 

 up to the limit given by static friction may be locally engendered during 

 periods of adhesion and then relieved by momentary slipping, with 

 sliding friction onlv. 



i - 



Eesistance of Ice to Flo wage 



The crescentic gouge is a large disruptive scar on the face of a compact 

 jointless rock. Any hypothesis to account for it must provide great 

 force. The particular hypothesis here given, instead of appealing to the 

 ferential stress developed by the resistance of the ice to the forcing of a 

 boulder into it. It can not be true unless the ice has great power )f 

 resistance to flowage; and, conversely, if it is true, the ice has greater 

 power of resistance than some students have been disposed to admit. It 

 is generally understood that cold ice is more rigid than ice at the melting 

 temperature, bnt the hypothesis is not concerned with cold ice. Doubt- 

 less crescentic gouges are made under cold ice, but the gouges preserved 

 for onr observation were not so made. Beneath the forward part of a 

 glacier the basal temperature is the temperature of melting (as condi- 

 tioned by the pressure) ; and as a great glacier wanes, every portion of the 

 bed is in turn subject to the action of its forward part. The finishing- 

 touches, therefore, the surface markings and the small details of sculpture, 

 can not be ascribed to ice of the low temperatures theoretically obtaining 

 far back under the neve. So the crescentic gouges, as explained, testify 

 to the resisting power of ice at the most favorable temperature for flowage. 



Whether we regard ice as a plastic substance, or whether we accept, as I 

 do, the view of Chamberlin, that it is made up of rigid crystalline grains 

 and flows chiefly by interstitial melting and regulation, we must recognize 

 a relation between velocity and resistance to flow. The more rapid the 

 flow the stronger the resistance. Therefore the crescentic gouges, if 

 they have been properly explained, may testify also to relative rapidity of 

 glacier movement. 



Nomenclature 



The word "gouge" connotes a process of formation analogous to the 

 work of a chisel. It is therefore inappropriate as the name of the dis- 



