948 HISTORICAL GEOLOGY. 



a mile and a half wide, enlarging southward to its junction with the Missis- 

 sippi valley; and, in contrast, the valley of the Mississippi north of this 

 junction is small. He thus obtained positive evidence that the valley and 

 river from Winnipeg southward was not long since one, and that the conti- 

 nental level was then such as would give the southward flow to the waters. 

 To reproduce now this slope would require a rise of the Winnipeg region 

 (or a sinking of the divide) amounting to about 260 feet ; and to give the 

 waters also a pitch of half a foot a mile, an additional 165 feet. The former 

 existence of this greater Mississippi is also shown by the fact that fresh- 

 water shells of the Winnipeg region also live in the Mississippi. 



Warren also suggested that Lake Michigan at the same time, owing 

 to the same northern uplift, discharged by the Illinois River into the 

 Mississippi — its broad and deep valley widening in the vicinity of the lake 

 in accordance with this direction of flow. 



The changes about all the Great Lakes were such as tended to give them 

 probably independent outlets. The channels that now unite them are all 

 shallow, generally not exceeding 50 feet. 



Further proof of high-latitude elevation in the Glacial period is afforded 

 by the river-valleys of the coast region now filled with water, that is the 

 fiords, and the multitudes of islands, and many channels among islands, along 

 fiord coasts. The fiords of Maine, Labrador, Newfoundland, Greenland, 

 British Columbia and Alaska, and those of Scandinavia, western South 

 America south of 41°, of Tasmania and South Australia, are such valleys, and 

 they all are confined to Glacial latitudes. None occur on southern Africa, 

 which reaches only to 34° 22' S. They were made when the land stood high 

 enough for the denudation of the rocky coast region ; and in view of the 

 great lift the continent and other continents were having in the Later Ter- 

 tiary time and during the opening Quaternary, it is a reasonable supposition, 

 as the author pointed out in 1856, that the work of excavation should have 

 gone forward during the Glacial period. It cannot be afiirmed that the work 

 of denudation was not begun during emergencies long before ; but if so, this 

 period of so widely extended elevation, probably the greatest in the world's 

 history, must have finished the work. 



Some of the fiords of the Atlantic coast between southern Maine and 

 Hudson Bay have been found by soundings, as stated by Spencer, to have 

 depths of 2000 to 3670 feet below the sea level ; and the St. Lawrence chan- 

 nel below the Saguenay has afforded soundings of 1104 and 1878 feet. The 

 Saguenay gorge descends 300 to 840 feet below the sea level and rises 1500 

 feet above it. They compare well with the fiords of the Scandinavian coast, 

 several of which are above 2000 feet in depth, and one, the Sogne Fiord, 

 4020 feet. 



The fiords of a coast differ widely in breadth and depth; and the deepest 

 and largest were probably those channels that had been excavated to the sea 

 level, during the time of emergence, while others are the shallower gorges 

 of the denuded region. They have generally at present a bottom of drift 



