0<— 



Diagram showing common granitic types of structure, whereby 

 declivities are easily removed by strong stream action. 



The peculiar relations existing between streams and 

 strengths of channel structures appear to have been over- 

 looked, otherwise there would never have been the long 

 and fruitless discussions concerning the ability of glaciers 

 to corrade and abrade, liven so late as 1909, one finds 



in the works of ;ui eminent mining authority. 1 



" An examination of our mod. -in glaciers shows us that a con- 

 siderable thickness of ire seems incapable of abrading or modifying 

 t<> any extent the surface over which it glides, even when carrying 

 a load of rock fragments locked in its undei surface. ... it is 



exert a pressure above the ultimate breaking strength of the schists. 



" None of the existing glaciers in New Zealand are capable of 

 excavating their beds, and it is doubtful if any in Europe or 



America are competent to do so It is equally certain that 



tee can only excavate its bed when the pressure of its mass exceeds 

 the ultimate crushing strength of the bed lock." 



It will be seen that Mr. Park's difficulty lies in the fact 

 that he is not here discriminating between the erosive 

 values of recent flood and present drought glaciers acting 

 along the same channel. The present inactivity of glaciers 

 in New Zealand is not due to the fact that they are unable 



' Park, James, " The Geology of the Queenstown Subdivision," Now 

 Zealand Geological Survey, Bull. No. 7, New Series, pp. 35 - 3U. 



