PREGLACIAL ELEVATION SHOWN BY FJORDS. 501 



floating iu isostatic equilibrium upon a plastic or molten interior, though 

 the vertical extent of elevation of the whole basin is probably several hun- 

 dred feet less than would be expected as a full measure of the weight 

 removed. Even with the presumption that the uplift in its rate of increase 

 toward the north is oidy approximately half, and in its aggregate amount 

 only a quarter pai't, or less, of what computation would require, this 

 hypothesis still seems to afford the best explanation that we are able to 

 offer for the northward ascent of these beaches, beyond such small por- 

 tion as can be referred to ice attraction. And it is to he observed that 

 glaciated areas generally show by their fjords that part of their depression 

 by the ice-sheet continues to the present time, not having been equaled by 

 the crustal elevation when the ice-sheet was dissolved. 



REVIEAV OF PLEISTOCENE OSCILIiATIONS OF LAND AND SEA. 



Having thiis examined the probable causes of the changes in relative 

 elevations within the area of Lake Agassiz, we shall gain nuicli further 

 knowledge of the evidence supporting the hypothesis concerning the earth's 

 crust and interior, to which it has led us, by reviewing the oscillations that 

 have affected various other parts of the world contemporaneousl}' with the 

 accumulation and disappearance of the Pleistocene ice-sheets. Fjords, 

 fossiliferous marine deposits, and migrations of animals and plants bear 

 important testimony of these vicissitudes of land and sea. It will be well 

 first to consider our own continent, and afterward to inquire whether South 

 America and Europe fared similarly. 



PREGLACIAL ELEVATION OF NORTH AMERICA SHOWN BY FJORDS AND 

 SUBMARINE RIVER VALLEYS. 



One of the most interesting fjords of North America is that of the 

 Saguenay, tributary to the St. Lawrence. Along a distance of about 50 

 miles the Sagueiuiy is from 300 to 840 feet deep below the sea-level; its 

 adjoining cliffs rise abruptly in some places 1,500 feet above the water; 

 and the width of its wonderfully sublime and picturesque gorge varies from 

 about a mile to 1^ miles.^ This fjord, like the many which indent our 



'J. W. Dawsou, Notes on the Postplioceue Geology of Canada, 1872, p. 4L 



