CHAMPLAIN SUBMERGENCE SHOWIS^ BY MARINE BEDS. 505 



Pacific soniewliat soutli of Vancouver Island and Pnj];'et Sound. The thick- 

 ness of the ice in tlie region of tlie White jMountains and Athrondacks was 

 about 1 niik'; and Dana lias shown, from the directions of striation and 

 ti'ans])ortation of the drift, that its central portion over the Laurentide 

 ]ii^;hlands between Montreal and Hudson Bay hnd jjvobably a thickness 

 of fully 2 miles. In British Columbia, according to Dr. G. M. Dawson's 

 observations, it covered mountain summits 5,000 to 7,G40feet above the sea.' 



LATE GLACIAL OR CHAMPLAIN SUBMERGENCE SHOWN BY FOSSILIFEROUS MARINE 

 BEDS OVERLYING THE TILL. 



While thus heavih" ice-laden, nearly the whole glaciated area of North 

 America sank below its present level, but for the most part only to a slight 

 amount in comparison Avith its previous elevation. Beginning at or near 

 a line drawn northeastward through New York City, Boston, and Nova 

 Scotia, the extent of the submergence of the land by the sea at the time 

 of the recession of the ice-sheet, as shown by fossiliferous marine deposits 

 overlying the till, increased from 1.50 feet in southeastern New Hampshire, 

 and 200 to 300 feet on the coast of Maine and New Brunswick, to 375 feet 

 on the St. Lawrence opposite to the mouth of the Saguenay, and 560 feet at 

 Montreal. It was 300 to 400 feet, increasing from south to north, in the 

 basin of Lake Champlaiu; about 275 feet at Ogdensburg, and 450 feet 

 near the city of Ottawa; and 300 to 500 feet, likewise increasing northward, 

 on the country southwest of James Bay." In Labrador the submergence 

 was of small amount at the south, adjacent to the Gulf of St. Lawrence 

 and Newfoundland; but was about 1,500 feet at Nachvak, near latitude 

 59° N., according to Dr. Robert Bell;^ and in northern Greenland and in 



' Geol. M.agazine (3), Vol. VI, 1889, pp. 350-352. Trausactious, Royal Socii'ty of Canada, Vol. VIII, 

 Sec. IV, 1890, pp. 31, 32. 



■2 A. S. Packard, jr., Memoirs, Boston Soc. Nat. Hist., Vol. I, pp. 231-2G2. .J. W. Dawson, Notes 

 on the Postpliocene (Jeology of Canada; and Am. Jour. Sci. (3), Vol. XXV, 1883, pp. 200-202. C. H. 

 Hitchcock, Proc, A. A. A. S., Vol. XXII, 1873, pp. 169-175; Geology of New Hampshire, Vol. Ill, pp. 

 279-282; and Geol. Magazine (2), Vol. VI, 1879, pp. 248-250. G. H. Stone, Am. Jour. Sci. (3), Vol. XL, 

 pp. 122-144, Aug., 1890. R. Chalmers, Transactions of the Royal Society of Canada, Sec. IV, 1886, pp. 

 139-145. Baron Ger.ard de Geer, Am. Geologist, Vol. IX, pp. 247-249, April, 1892; and Proc, Boston 

 Soc. Nat. Hist., Vol. XXV, 1892, pp. 4.54-477. Warren Upham, Proc, Boston Soc. Nat. Hist., Vol. 

 XXIV, pp. 127-141, Dec, 1888; Am. .lour. Sci., May, 1889. 



^Bulletin, G. S. A., Vol. I, 1890, p. 308. 



