G PROCEEDINGS OF ROCHESTER MEETING. 



to the ice-flow the slip appears to have been divided between the valley-bottom 

 and the plane connecting its walls. 



Mr Warren Upham said — 



Instead of attributing the courses of glaciation in the Connecticut valley to a local 

 glacier, as suggested by Professor Hitchcock, my observations of the glacial drift in 

 thai valley and over the adjoining country lead me to think that the striae bearing 

 toward the south and west of south are due to local deflection of currents of the 

 ice sheet during the time of its departure, rather than either to any glacier later- 

 existing there or to longer continuance of a remnant of the ice sheet there than on 

 the higher land at each Hide. The Connecticut valley esker (called a kame in 

 Geology of New Hampshire, volume iii) was traced by Professor Hitchcock and 

 myself along the axis of this part of the Connecticut valley for a distance of about 

 twenty-five miles, from Lyme. New Hampshire, to Windsor, Vermont. It is 

 believed to have been deposited in the ice-walled channel of a superglacial stream 

 near its debouchure from the ice sheet to the land from which the ice had retreated. 

 The size and extent of this esker and its material, which is obliquely bedded gravel 

 and sand without bowlders, show that it was formed by a large superglacial river 

 draining a considerable area of the melting ice sheet. When the ice had become 

 thinned by ablation, its surface here descended from each side toward the glacial 

 river by which the esker was being formed, and there was probably also some 

 indentation orembayment of the receding glacial boundary at the river's mouth in 

 the valley. At this time the currents of the ice sheet which had passed southeast- 

 ward even in the bottom of the valley, as known by the oldest sets of strife there 

 noted by Professor Hitchcock, became deflected, as I think, toward the south and 

 west of south, taking the course of the valley, in obedience to the law that the 

 currents of the outer part of the ice must everywhere turn perpendicularly' toward 

 its edge. 



Professor Niles added — 



The Alpine glaciers suggest a relation between ice and topography quite different 



from that assumed by Mr Upham. During past ages glaciation was much more 

 extensive in the Alps than at present ; yet as the ice retreated, it did not withdraw 

 from the valleys but disappeared from the divides and shrank into the valleys ; 

 and to-day, as probably at every stage since the Alpine ice reached its greatest ex- 

 tension, the margin of the ice is not indented by notches coinciding with the val- 

 leys, but is marked by streams of flowing ice pushing far below the general snow 

 level. 



Mr McGee added— 



While analogies drawn from Alpine glaciers are of great use in researches con- 

 cerning ancient glaciers of this country, it should be borne in mind that ice-work 

 is not necessarily similar in regions of high relief like 1 the Alps, and in regions of 

 low relief like the plains of | he Mississippi valley and perhaps also the plateaus of 

 New England. In regions of high relief the terrestrial surface is rugose and the 

 general flow of the ice is obstructed by the inequalities. Accordingly, while the 



