1 in R. S. TARR — GLACIATION OF MOUNT KTA.\I)N\ MAINE 



glaciers from the highlands of the United States with those of Canada 

 produced one large ice-cap, which advanced over New England even to 

 the sea. This continental ice-sheet, rising higher and higher on the 

 mountain sides, finally enveloped even the loftiest and steepest peaks. 



Of this earlier set of local glaciers no evidence has been found, and it 

 is doubtful if much exists ; for, with the activity of later ice erosion, that 

 of the continental glacier and the succeeding local glaciers, the signs of the 

 primary local glaciers would have been in large part, if not completely, 

 erased. Concerning the advance of the ice of the great continental glacier, 

 until it overtopped even the highest mountains, sufficient evidence has 

 been brought forward, as was stated in the first part of this paper. 



The period of continental glaciation in New England must have been 

 of considerable duration, for there is everywhere distinct evidence of ice- 

 scouring on the mountains which projected into the ice-sheet. This is so 

 pronounced as to constitute a prominent element in the topography of 

 Maine. It was noticed by Thoreau, and has been mentioned by many 

 other writers, that the northern slopes of the hills and mountains are 

 often moderate, while the southern slopes are steep. In some cases this 

 is evidently due to structural peculiarities in the rock-masses forming 

 the mountains ; but elsewhere it is entirely independent of this, and no 

 other explanation than ice-scouring seems rational. 



One who has studied this aspect of the action of the Greenland con- 

 tinental glacier is prepared for just such a modification of topography. 

 For instance, in the mount Schurman nunatak* the ice has passed up 

 the stoss slope and scoured and smoothed it perceptibly, while the west, 

 or lee, slope is a precipice against which the ice is doing almost no work. 

 The various mountains along the Greenland coast again and again illus- 

 trate the same characteristic of form, even when entirely outside the 

 limit of present ice erosion. This is noticeably the case in the mountain 

 called the "Devil's Thumb" on the Ryder map.f In Maine instances 

 of this are so numerous as not to need specific mention. They are seen 

 on all hands, and are often so evidently out of relation to rock structure 

 ,as to seem to demand the explanation of glacial erosion. 



Following the long stage of continental glaciation, there came a shrink- 

 ing of the ice. Then some of the New England peaks, such as Ktaadn 

 and Washington, rose so high that they projected above the surface as 

 nunataks, reaching higher and higher above the ice-sheet, as the glacier 

 melted, until a sufficient area of country was exposed to permit the 

 accumulation of snow fields, with valley glaciers descending from the 

 mountain tops. With the withdrawal of the great ice-sheet there again 



*Tarr : Amer. Geologist, vol. xx, 1897, p. 147. 

 t Bull. Geol. Soc. Am., vol. 8, 1897, p. 254, 



