524 THE JOURNAL OF GEOLOGY. 



of these till billows are usually distributed parallel to the margin 

 of the ice, and to that extent conform to the habit of terminal 

 accumulations. I have thought that they might be an inter- 

 mediate form between submarginal moraines and drumlins, but, 

 while they unquestionably graduate into the former, I have never 

 observed their graduation into the latter. It seems, therefore, 

 probable that they should be removed from this division and 

 placed below. 



(e) Irregular till hills. — Besides the above forms which show 

 a tendency to some definite law of development, there is a con- 

 siderable class of aggregations of till that seem to pay no 

 respect to laws of symmetry or to systematic principles of 

 growth. At present no classification seems tenable except one 

 based upon their very irregularity. 



( 3 ) . Submarginal ridges of till parallel with the ice border. — Both 

 the till sheets (i) and the subglacial aggregates (2) that have 

 been described above occupy territory extending for considerable 

 distances back from the border of the ice, indeed, ideally the 

 first class may be regarded as covering the entire territory 

 occupied by the ancient glacier. On the contrary, the ridges of 

 till here considered lie along what was the immediate border of 

 the ice at certain of its stages. They are thought to have been 

 formed under the edge of the ice, but it remains to be deter- 

 mined to what an extent they were accumulated under the im- 

 mediate border of the ice and to what an extent they were 

 deposited at the distance of one, two, or three miles from the 

 precise edge of the glacier. It does not seem at present possi- 

 ble to determine, or at least it does not seem to have been 

 determined, whether the whole of the accumulation was built up 

 simultaneously throughout its entire breadth, or whether the 

 outer portion was accumulated under the immediate edge of the 

 ice and the inner portions built up a little later in like manner 

 under the edge of the ice when it had withdrawn somewhat. 

 These ridges are from one to a few miles wide, are composed 

 essentially of till (though assorted material ma} r form a greater 

 or less constituent), possess in the main a gently flowing contour 



