GLACIATED AREAS UPLIFTED AS PLATEAUS. 125 



haps nearly the same; and to the Catskills the apparent ascent was onlv 

 30 feet per mile for the distance of 100 miles |from the ice border. But in 

 Greenland all of the four journeys on the inland ice find it to ascend 

 with much steeper slopes, attaining the altitude of the summit of Mount 

 Washington at distances which vary from 50 to 125 miles from its edge. 

 Nor does the less area of the Greenland ice explain its steeper gradients, 

 for it probably has a length of more than 20 degrees from south to north, 

 or over 1,400 miles, with a width of 200 to 600 miles, and an area of 

 about 600,000 square miles, or one-seventh as much as the later ice-sheet 

 of North America. 



Apparently the conditions for outflow of the ice from this area are 

 similar and equally favoralile wi'th those which prevailed on our continent 

 in the Glacial period. The comparison therefore suggests that the ])reseut 

 elevation of the glaciated portion of this continent is probablv much 

 changed from that which it had during its epochs of glaciation. If the 

 North American ice-sheet during its stages of growth and culmination 

 attained steep slopes and liigli altitudes near its Ijorders comj)arable 

 with the Greenland ice, the records of glaciation on our mountains show 

 that during the time of accumulation of the ice and until it attained its 

 maximum extent the glaciated area was uplifted as a high continental 

 l)lateau, with the same principal topographic features of mountains, 

 valleys, and g-eneral contour as in preglacial and postglacial times, but 

 having in its outer 10() or 200 miles slopes of probablv 20 to 30 feet 

 per mile, descending from the plateau of the interior of the ice-enveloped 

 country to its margin.^ 



Similar u])lifting seems also to have affected the glaciated northwestern 

 portion of Europe, for there, too, the slopes and height of the limits of the 

 drift resemble those of North America rather than the Greenland ice-sheet. 

 Prof James Geikie finds that the surtace of the ice which moved westward 

 from northern Scotland across the Minch and the Hebrides had a descent 

 of 25 feet i)er mile; "but slight as that incline was," he remarks, "it was 

 probablv twice as great as the slope of the mer de glace that filled uj) the 

 German Ocean."^ Mr. T. F. Jamieson therefore concludes that when the 



' The Ice Age in Xorth America, p. 595. 



-Quart. Jour. Geol. Soc, Vol. XXXIV, y. 681, Xov., 1868. 



