CHAPTER Y. 



THE DENUDANTS OF THE EARTH'S SURFACE ICE 



ACTION. 



GLACIAL denudation, seemingly, ought to be con- 

 sidered a different action to meteoric abrasion, as 

 these two forces work so differently. A glacier has 

 been said to belong to the atmospheric denudants, as 

 it is a river of ice, formed from snow ; but compare the 

 work a glacier and its tributaries can do with that of a 

 river and its tributaries. The tributaries of the first 

 are beds of snow and ice, while those of the latter 

 are all the chemico -fluvial forces combined. The 

 glacier and its tributaries work altogether by 

 mechanical action, being confined to planing and 

 triturating rock, and quarrying, by tearing off masses 

 of rock ; while the chemico-fluvial denudation is due 

 to chemical and mechanical action combined. The 

 latter is quite different to that exercised by ice, in 

 this respect, that it is principally carrying away 

 materials loosened by chemical action, the only 

 trituration it accomplishes being that done in river- 



