associated with Glaciation. 115 



during the ice-sheet. The belief that this uplift was 3,000 

 feet or more, giving sufficiently cool climate, as Prof. T. G. 

 Bonney has shown, to cause the ice accumulation, has been 

 only reached within the past few years by Spencer, LeConte, 

 Hilgard, and the present writer, through the discoveries by 

 soundings of the IT. S. Coast Survey, that on both our Atlantic 

 and Pacific coasts submarine valleys evidently eroded in late 

 Tertiary and Quaternary time reach to profound depths, 

 2,000 to 3,000 feet below the present sea level.* 



Although the adequacy of the preglacial epeirogenic uplift 

 of this continent to produce its Pleistocene ice-sheet was 

 tardily recognized and cannot yet be said to be accepted by all 

 American glacialists, it was distinctly claimed by Dana in 1870 

 that the Champlain subsidence of the land beneath its ice- 

 load, supposing it to have been previously at a high altitude, 

 must have brought climatic conditions under which the ice 

 would very rapidly disappear. The depression would be like 

 coming from Greenland to southern Canada and New England. 

 In Professor Dana's words : " Such an extended change of 

 climate over the glacier area was equivalent, in eifect to a trans- 

 fer from a cold icy region to that of a temperate climate and 

 melting sun. The melting would therefore have gone forward 

 over vast surfaces at once, wide in latitude as well as longi- 

 tude.'^ 



Such explanations as these accounting for the gradual accu- 

 mulation and comparatively rapid dissolution of the North 

 American ice-sheet are also found to be applicable to the ice- 

 sheets of other regions. The fjords of the northern portions 

 of the British Isles and of Scandinavia show that the drift- 

 bearing northwestern part of Europe stood in preglacial time 

 1,000 to 4,000 feet higher than now, while on the other hand 

 late glacial marine beds and strand lines of sea erosion testify 

 that when the ice disappeared the land on which it had lain 

 was depressed 100 to 600 feet below its present height, or 

 nearly to the same amount as the Champlain depression in 

 North America. Again, just the same evidences of abundant 

 and deep fjords and of marine beds overlying the glacial drift 

 to heights of several hundred feet above the sea are found in. 

 Patagonia, as described by Darwin and Agassiz. On these 

 three continental areas, the widely separated chief drift-bear- 

 ing regions of the earth are found to have experienced in con- 

 nection with their glaciation in each case three great epeiro- 

 genic movements cf similar character and sequence, first, a 



* Detailed notes of these submerged valleys are presented in my payer "On the 

 Cause of the Glacial Period," Am. Geologist, vol. vi. pp. 327-339, Dee.. 1890. 



f Trans. Conn. Acad, of Arts and Sciences, vol. ii. 1870, p. 67. Compare this 

 Journal, III. vol. x. pp. 168-183, Sept.. 1^73. 



