5W 



CENOZOIC TIME. 



of the Great Lake region may have sent off floating masses down the 

 Mississippi valley, as well as to parts of the present prairie region of 

 Ohio, Indiana, and Illinois. 



The facts teach, that the region of the Great Lakes was probably 

 one immense lake, as held by Newberry and others, and that the 

 waters spread far south, over the States of Ohio, Indiana, and Illinois, 

 and discharged from Lake Erie and Lake Michigan into the Missis- 

 sippi valley, so that there was abundant opportunity for transportation, 

 by means of floating ice, from the Glacier to the Gulf. We gather 

 also that the Mississippi waters of the Champlain era, below the mouth 

 of the Ohio, had an average breadth of fifty miles, and, along by Ten- 

 nessee and northern Mississippi, of seventy-five miles ; so that it was in- 

 deed a great stream. In the Glacial period, the era of erosion, it was 

 deepening its bed, through the Paleozoic, Cretaceous, and Tertiary 

 rocks; but, in the Champlain, when the land to the north was de- 

 pressed, the river filled full the wide valley, and made its great breadth 

 of Champlain deposits. All the other rivers of the continent, alike 

 augmented, were at the same work, each according to its capacity. 

 The Connecticut River south of Northampton had two great channels 

 thence to the Sound, both 80 miles long, and 100 feet or more in 

 depth (the old one 150 to 200 feet) the most of the way ; while the 

 new western one emptied into New Haven Bay by two river-courses, 

 those of Mill River and the Quinnipiac. (Am. Jour. Sci., III. x. 477.) 

 The Champlain period, in the world's history, was preeminently the 

 era of fresh-water formations. 



Other geographical changes from the Champlain flood consisted in 

 the filling up of old river-channels with drift, and forcing the streams 

 to open new ones. There is an old gorge of Niagara River, commen- 

 cing at the Whirlpool, which was thus filled. It is probable that, when 

 the damming by Drift was accomplished, the waters of Lakes Erie and 

 Ontario were on a common level, so that there was no river-flow to 

 prevent the catastrophe ; and that, when the elevation that ended the 

 Champlain era began, the river first found out that its old channel was 

 gone. The stream, then renewing its flow, began, at the Queenstown 

 heights, the present cut through the rocks to the Whirlpool (p. 590). 



Dr. Newberry has stated that the Ohio River formerly had a more southern channel 

 around the Falls, near Louisville, and lost it, in a similar way, in the Champlain period; 

 that formerly Lake Huron discharged into Lake Erie by a more easterly channel than 

 the present one, and was forced in this era to take the route over the rocks. The chan- 

 nel of discharge, from Lake Michigan to the Mississippi, which F. H. Bradley has 

 pointed out as having been made or used in the Glacial period, he shows was filled up 

 in the Champlain, and then the more western channel, from Chicago along the Des 

 Plaines to the Illinois, became the outlet, and continued to be so until the elevation 

 opening the Recent period. 



