RELATIONS TO ISOSTASY 327 



as a whole, althougli the relief from load was almost confined to the 

 north and south and amounted to little or nothing at the center. 



One may draw the conclusion that the earth's crust can sustain 

 inequalities of load amounting to 1,500 or 2,000 feet of ice, or the equiva- 

 lent w^eight of rock, where the width of the region in question is not 

 greater than 75 miles, the load decreasing from a maximum at the two 

 sides to nothing in the center. 



The lack of differential elevation in the Gaspe Peninsula may be con- 

 trasted with the doming up of Newfoundland after the Ice Age, as indi- 

 cated by Tyrrell and Fairchild. Newfoundland is considered to have 

 been an independent glacial center, and the isobases are so mapped as to 

 show a doming of the interior of 400 feet as compared with the edges. 

 This may be interpreted as meaning that Newfoundland bore an ice-cap 

 1,200 or 1,500 feet thick, diminishing in all directions outward — condi- 

 tions exactly opposite to those in Gaspe, where the central mountains 

 carried little or no ice, though local glaciers radiated out from them. 



Newfoundland has diameters of about 300 miles by 200, and a land 

 area of 42,000 square miles, and it seems that a portion of the earth's 

 crust of those dimensions does not change its level as a whole, but under- 

 goes differential elevation to correspond to the varying relief from load; 

 or, to put it in another way, the earth's crust is not strong enough to resist 

 isostatic adjustments where the area affected is 200 miles wdde, but can 

 support the difference of load where the width is only 75 miles, as in 

 Gaspe. 



The case of the Torngat region, in northeastern Labrador, is apparently 

 similar to that of the Gaspe Peninsula, though it has been studied much 

 less thoroughly. Tlie breadth of the unglaciated core of mountain and 

 tableland is probably 50 or 60 miles, but 30 miles of the eastern side of 

 the Torngat Range is riddled with fiords and deep valleys, occupying 

 probably half tlie surface. As these were once filled with great local 

 glaciers reaching in places 2,000 feet in thickness, the amount of depres- 

 sion of the region, about 250 feet, is readily accounted for. There is no 

 evidence that the glacier-laden coastal region has risen more than the 

 unglaciated tableland, perhaps 20 or 30 miles wide toward the west. 



The suggestion of De Geer that the pre-Cambriah shield rose, as con- 

 trasted with stationary Paleozoic terranes to the south, receives no support 

 from the actual changes of elevation shown by beach levels. The highest 

 actually measured elevation, 690 feet at Kingsmere, north of Ottawa, is 

 on Archean territory; but the beach levels diminish to 225 feet, still on 

 the pre-Cambrian, at Komaktorvik Fiord, in the north of Labrador. To 



