EFFECTS OF GLACIAL WEARING 1 79 



glacial work has been very extensively done in recent geo- 

 logic time. It is indeed characteristic of glacial wearing, as 

 distinguished from the erosion effected by flowing water, that 

 the ice can carve out depressions in the rock. If we examine 

 any considerable area which was worn by ice, we find every- 

 where pits upon its surface, which may be from a few feet to 

 a hundred feet or more in depth. Owing to the essential 

 plasticity of ice it can, when moving in the manner of a 

 glacier, descend into and rise up from tolerably deep depres- 

 sions ; it will, indeed, deeply carve out any soft portion of 

 rock which it may encounter, leaving the surrounding 

 materials as a rim to the basin. \\ hile it is true that onl\' 

 a small part of the lakes which beset the glaciated countr\- of 

 North America are due to the fact that the water is contained 

 in basins completely surrounded by firm-set rock, there can be 

 no question that there are thousands, if not tens of thousands, 

 of such cavities on the glacially worn surface of this countrw 

 It is a noteworthy fact that the form of the fiord basins 

 is essentially the same as that of our glacial lakes wliich 

 are surrounded by rock margins. The fiords, which are 

 characterized by a sill or barrier rising to near the surface 

 of the water on their seaward side, may be regarded as 

 basins essentially like those which are occupied by the rock- 

 bordered lakes, the outer margins of which are slightly 

 submerged below the level of the sea. The fact that these 

 basins are due to rock-carving and in no considerable meas- 

 ure to river action is clearly shown, as I have elsewhere 

 indicated, by the arrangement of the fiords on the islands of 

 Mount Desert, Maine." To a certain extent these basin- 



* See Geology of Mount Desert, Eighth Annual Report United States Geo- 

 logical Survey, pp. 1005-1009. 



