THE CAUSE OF THE GLACIAL PERIOD. 501 



Accompanying the subsidence of ice-loaded areas, there were 

 doubtless uplifts of contiguous regions, perhaps sometimes in- 

 cluding outer portions of the country glaciated. For example, 

 the Quatenary elevation of which Le Conte finds evidence in 

 the Sierra Nevada and northward may have been contempora- 

 neous and correlative with depression of the northern parts of 

 the continent beneath its ice-sheet. Furthermore, instead of 

 being wholly offset by deformation of the crust, the glacial 

 depression may have produced also extensive extravasation of 

 lava, as is suggested by Jamieson * and Alexander Winchell,f 

 for the vast Quaternary lava-flows of California, Oregon, Wash- 

 ington, and a large adjacent region. As Jamieson well re- 

 marks, this result would tend to cause a permanence of part of 

 the depression of the ice-covered area. However it may have 

 been caused, probably such permanent Quaternary subsidence 

 is true for the coasts of many glaciated countries, as shown by 

 fiords, and for the basins of the Lauren tian lakes, which, ex- 

 cepting Erie, are depressed several hundred feet below the level 

 of the ocean. 



One of the most interesting fiords of North America is that 

 of the Saguenay, tributary to the St. Lawrence. Along a 

 distance of about fifty miles the Saguenay 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 one mile and a half. J This fiord, like the many 

 which indent our Eastern coast from Maine to Labrador and 

 Greenland, and our Western coast from Puget Sound to the 

 Arctic Ocean, was eroded by a stream that flowed along the 

 bottom of the gorge when it was above the sea ; and this erosion 

 was probably going forward in the epoch immediately preced- 



problems of ice attraction and of deformation of the earth's crust have been 

 farther discussed by President Chamberlin before the Philosophical Society of 

 Washington, March 13, 1886; and, jointly with Professor Salisbury, in the 

 " Sixth Annual Report, United States Geological Survey," pp. 291-304. 



* " Geological Magazine, 1 ' II, vol. ix, 1 882, p. 405. 



f " American Geologist," vol. i, pp. 139-143, March, 1888. 



% " J. W. Dawson, " Notes on the Post-Pliocene Geology of Canada," 1872, 

 p. 41. 



