GLACIERS OF THE CANADIAN ROCKIES AND SELKIRKS. US 



a vertical distance of some 2,000 feet and accumulating along the base of the 

 cliff. The ice of the glacier is broken into fragments, some of it disintegrating 

 into its component granules and much of it ground into ice dust, destroying 

 completely the stratification and lamination of the hanging glacier. The ava- 

 lanches occur mainly during the late spring, summer, and early fall, and as a 

 result of the spreading of the fragments from sliding and rolling there is made 

 each season a stratum of ice similar to those ordinarily found in the n6v6 region. 

 Regelation is complete and there arises what is known as a reconstructed, or 

 regenerated glacier, with its strata Leading to and dipping towards the region 

 of accumulation. The weight of the ice here forces the lower strata to move 

 out at right angles to the cliff face and a forward movement is imparted to the 

 ice directly across the Mitre Glacier upon which it rests. This regenerated Lefroy 

 moves about one-half as fast as the underlying Mitre, so that before the latter has 

 reached the Victoria, the Lefroy has crossed to the opposite side of the valley. 

 Between the hanging Lefroy Glacier and its bed there is being manufactured a cer- 

 tain amount of ground-morainic material, which is incorporated into the strata 

 of the regenerated Lefroy, and moved across the valley as a result of its motion. 

 While this is taking place, however, the Mitre is carrying the entire Lefroy down 

 the valley and the actual motion of the debris is the resultant of these two 

 motions by which there is accumulated at the base of Mt. Aberdeen a great heap 

 of ground-morainic matter, with a dressing of angular material from the face of 

 the latter mountain. The ground moraine rests upon the back of the Mitre 

 and some of it is ridged parallel with its side, in which form it is dealt out to 

 the Victoria and constitutes the main bull<: of its right lateral moraine. This 

 Lefroy Glacier is distinct from the Mitre, upon which it rests, in that it is a differ- 

 ent type, is nourished diffei-ently, has a different form, a distinct set of strata 

 unconformable with those of the Mitre, has a different direction of motion, a dif- 

 ferent rate of motion, and is accomplishing a wholly different geological work. 

 The glacier is parasitic in the sense that it is carried by its host and is nourished 

 from snow and ice that might otherwise be available for it. It is not parasitic in 

 the sense that it draws its sustenance from the Mitre itself. 



It is probable that glaciers of this type are now, and have been, more common 

 than has been generally recognized. It seems likely that at a certain stage the 

 glacier in a hanging valley would svistain more or less of this relation to the trunk 

 glacier. By means of such a glacier we may account for the lateral transporta- 

 tion of materials across a valley and a transportation that would leave no record 

 upon the bedrock. If two distinct glaciers may occupy the same valley simul- 

 taneously, it seems probable that two ice sheets of the continental type might 

 be superposed, flowing in different directions, the upper delivering material to 

 the lower. 



5. Bear-den Moraines. 

 The bear-den type of moraine is so exceptional that some special explanation 

 must be found by which we may account for the accumulation of coarse mountain 



