44 JJjpharn — Review of the Quaternary Era, 



tween Montreal and Hudson bay, as is indicated by the general 

 divergence of striae and dispersal of drift from that area. 

 This ice-sheet was probably 6,000 feet thick over Reindeer and 

 Winnipeg lakes, but westward it declined to its outermost 

 terminal moraine east of the Hand, Cypress, and Sweet Grass 

 hills, which had been islands surrounded by ice during the 

 the earlier glaciation. In the far western Cordilleran region, 

 however, the ice of the second and third Glacial epochs prob- 

 ably nearly equalled, or in some portions exceeded, that of the 

 first. While the second glaciation fell short of the earlier in 

 the Mississippi basin and on the great plains, it passed beyond 

 that on the Atlantic coast ; and likewise, with the third glacia- 

 tion, it covered and obliterated most of the earlier glacial 

 records in the Rocky Mountains and westward. Throughout 

 the drift-bearing area traces of the last glacial movements, and 

 of the conditions attending the retreat of the latest ice-sheet, 

 are much better preserved than those of preceding stages in 

 the Glacial period ; and similarly the relative levels of land 

 and sea at the time of disappearance of the ice are displayed 

 very clearly. 



Jamieson twenty-five years ago suggested that the ice of the 

 Glacial period might cause a subsidence of the earth's crust 

 beneath it, because of the pressure of its immense weight, the 

 crust being supposed by him to rest, in accordance with the 

 laws of equilibrium of flotation, upon the heavier molten 

 interior of the earth. * Subsequent researches of glacialists 

 strongly support this opinion, for most countries that have been 

 ice-covered, though previously much elevated, are found to 

 have stood lower than now in relation to the sea level when 

 the ice disappeared, since which time they have risen to their 

 present height. In the interior of this continent the depres- 

 sion of the land beneath the ice-sheet of the first Glacial epoch 

 is shown by the loess of the Missouri and Mississippi basins, 

 which seems to be a deposit of broad, slackened river floods 

 and of shallow lakes adjoining the ice-front. On the Atlantic 

 coast the Champlain subsidence attending the close of the 

 second Glacial epoch is known, from fossiliferous marine beds 

 overlying the till, to have been slight in northeastern Massa- 

 chusetts, 150 to 230 feet in Xew Hampshire and Maine, noth- 

 ing or of small amount in Xova Scotia, but considerable, with 

 increase from east to west, along the lower Saint Lawrence 

 valley, being 375 feet opposite the Saguenay, and 520 feet at 

 Montreal, but thence diminishing southward along lake Cham- 

 plain and westward in the upper Saint Lawrence and Ottawa 

 valleys. The country southwest of Hudson bay sank 300 to 

 500 feet, Labrador 1,000 to 1,500 feet, and western Greenland 



* Quart. Jour. Geol. Soc. London, vol. xxi, 1865. p. 178. 



