510 THE GLACIAL LAKE AGASSIZ, 



and 400 feet) withiu the period of the now existing shells. The old and 

 weathered shells left on the surface of the upraised plain still partially 

 retain their colors." ^ Another evidence of the recency of the uplift is sup- 

 plied by the discovery by Agassiz of a saline lakelet about 150 feet above 

 the sea, in which several species of marine mollusks were found living, 

 identical with those of the neighboring seashores. - 



Northwestern Europe also had a much greater altitude during the 

 later part of the Tertiary era, in which the land suffered vast denudation, 

 with erosion of fjords and channels that are now submerged hundreds and 

 even thousands of feet beneath the sea. About the northern parts of the 

 British Isles the depths of the submarine channels of the old land surface 

 are approximately from 500 to 8 00 or 1 , 000 feet. ^ The Skager Rack, between 

 Denmark and Norway, has a depth of 2,580 feet, with a still deeper sub- 

 merged valley running from it west and north to the abyssal Arctic Ocean.* 

 On the coast of Norway the depth of Christiania fjord below the sea-level 

 is 1,380 feet; of Hardanger fjord, 2,624 feet; and of Sogne fjord, the longest 

 in Norway, 4,080 feet." The preglacial altitude of these portions of the 

 European glaciated area was therefore from 1,000 to 4,000 feet higher than 

 now. Probably many of these submarine chamiels are more or less filled 

 with the glacial drift, so that valleys originally descending continuously 

 toward the margin of the continental plateau have become in some portions 

 changed to inclosed basins. Another and more probable explanation of 

 the much greater depth of some of the fjords in their inland portion than 

 at their mouths is the depression of the country while it was ice-covered, 

 the coast having subsided much less than the interior. 



At the close of the Ice age in Europe, as in America, the glaciated 

 areas were mostly depressed somewhat below their present height. The 

 supposed great submergence, however, up to 1,200 or 1,500 feet or more, 

 which has been claimed by British geologists for northern Wales, north- 

 western England, and a part of Ireland, on the evidence of marine shells 



' Voyage of the Beagle, Chapter VIII. 



2 Louis Agassiz : His Life aud Correspondence, Vol. II, p. 716. 



3 James Geikie, Quart. Jour. Geol. Soc, Vol. XXXIV, 1878, PI. XXXIII; The Great Ice Age, 

 2d ed., pp. 279-284, Pis. IX-XII. 



■• Nature, Vol. XXIII, p. 393, with map of submarine contour. 



£■ T. F. Jamiesoa in Geol. Magazine (3), Vol. VIII, pp. 387-392, Sept., 1891. 



