248 w. D. WILCOX 



The phenomena of crag and tail, like the drumlins, are very 

 constant and no less important in determining the direction of 

 the ice movement. Crag and tail assumes all gradations between 

 ridges several miles in length to those that are merely shallow 

 accumulations of drift in the lee of slight elevations of the rock 

 surface. 



Fig. i.— Section near Banff showing two tills. 



Terminal moraines, except near existing glaciers, are far less 

 frequent than the subglacial drift formations. Modified drift and 

 river terraces are well marked on all the rivers as soon as they 

 reach the plains; also in. the mountain valleys of the Athabasca, 

 Saskatchewan, and Columbia ; but the smaller rivers and streams 

 rarely show well defined terraces in the mountains themselves. 



