66 THE DENUDANTS OF 



a glacier, after working for years, cannot grind out 

 scratches not the tenth of an inch in depth, how has 

 it been able to form the roches moutonnees or ice- 

 dressed hummocks ? These, however, were princi- 

 pally formed when the ice first occupied the country 

 and the action of the glacier was at its maximum, 

 carrying away the weathered and softened portions of 

 the rocks. If we examine a weathered mass of rock, 

 we find that the atmosphere has affected it more or 

 less deeply, the lower margin of the weathered por- 

 tion being a line made up of a series of curves that are 

 abrupt, if there are sharp inequalities on the surface 

 of the rock, but are gentle if the surface is even or 

 nearly so. If an abrader such as ice were to attack 

 such surfaces, the weathered portion would be quickly 

 removed and leave a flowing outline similar to that 

 of an ice-dressed hnmmock. A second ice, passing 

 over such a surface, would have no weathered portions 

 to remove ; consequently it could not abrade the 

 surface like its predecessor, or obliterate all the 

 scratches and ruts produced during the passage of 

 the first sheet of ice. 



A glacier when it first occupies a country is charged 

 with the detritus due to weathering, and if it dies 

 out previous to all this contained matter being 

 carried away, the country it occupied will be 

 covered by hummocks of rocky moraine drift, as 

 proved by King in his explorations of the dying out 



