GLACIATED AREA EXCEEDS 4,000,000 SQUARE MILES. 207 



Strait of Juan de Fuca and Vancouver island northwestward to the vicinity of 

 the Copper river and Prince William's sound.* But most of Alaska and a 

 portion of the adjacent Northwest Territory of Canada had too little snowfall 

 or were otherwise affected by climatic conditions unfavorable for glaciation. 

 The northwestern limit of the continental ice-sheet, as determined by Rus- 

 sell ,t McConnelljJ and Dawson,§ passes northeastwardly from the Coast 

 ranges about Mount St. Elias, to cross the Yukon and Pelly near the me- 

 ridian 136° 15', and thence extends nearly due north to the Arctic ocean 

 close west of the mouth of the Mackenzie. 



The scanty observations which have been gathered in the Arctic archipel- 

 ago, concerning the transportation of drift from the Archean area of the 

 Northwest Territory northward to Baring land, from the region of the Cop- 

 permine river northward to Prince of Wales strait, from North Somerset 100 

 miles or more toward the northwest and northeast, and from south to north in 

 Smith sound, 1 1 indicate that the greater part of this archipelago was enveloped 

 by the continental ice-sheet, and that from Baffin land, North Devon, Elles- 

 mere land, and Grinnell land, it was continuous eastward to the ice sheet of 

 Greenland. 



On the Atlantic coast it filled Hudson strait with an eastward outflow, as 

 determined by Dr. Robert Bell;^ Labrador was wholly ice-covered except- 

 ing the upper portion of the mountain range south of Cape Chidley, which 

 seventy miles from the cape attains an elevation of about 6,000 feet above 

 the sea ;** Newfoundland, enveloped by the farthest eastward portion of this 

 ice-sheet, was glaciated radially outward into the ocean on the north, east, 

 and south ;tt and thence southwestward the border of the ice-sheet, passing 

 beyond the shore-line of Nova Scotia, rested on the irregular submarine 

 ridges and plateaus of the Fishing Banks, which consist of Tertiary strata 

 more or less overspread with morainic drift deposits, extending from New- 

 foundland to Cape Cod and Nantucket. 



The part of North America and outlying islands thus enclosed, amounting 

 to more than 4,000,000 square miles, I believe to have been occupied by the 

 ice-sheet of the second Glacial epoch at its time of maximum area. In the 

 following discussion of the probable thickness of this ice-sheet, I shall en- 

 deavor to set forth my reasons for this belief, which differs from the opinions 

 of Mr. J. B. Tyrrell, who thinks that a narrow driftless tract borders the 



*G. M. Dawson, in Quart. Jour. Geol. Soc, London, vol. XXXVII, 1881, p. 278; Trans., Roy. Soc. 

 Can., vol. VIII, sec. IV, 1890, Plate II. 



t Hull. Geol. Soc. Am., vol. I, pp. 140, 146-8. 



X Ibid., p. 544. 



gGeol. and Nat. Hist. Survey of Canada, Annual Report, new series, vol. Ill, for 1887-88, pp. 132 B 

 and 149 B. 



II G. M. Dawson, Geol. and Nat. Hist. Survey of Canada, Annual Report, vol. IE, for 1886, pp. 56-58 R. 



i[Geol. and Nat. Hist. Survey of Canada, Report of Progress. 1882-84, p. 36 DD; Annual Report, 

 vol. IV, for 1888-89, p. Ill E. 



** A. S. Packard, Memoirs of the Boston Society of Natural History, vol. 1, 1866, pp. 219, 220. 



tt John Milne, Quart, Jour. Geol. Soc, London, vol. XXX, 1874, pp. 725-8. 



XL— Bull. Geol. Soc. Am., Vol. 2, 1890. 



