16 W. UPHAM — ICE AND KIVER EROSION IN SAINT CROIX VALLEY 



Feet 



Same at Moose River rapids 987 



Mouth of Namekagon river 912 



Mouth of Yellow river 892 



Mouth of Clam river 870 



Head of Kettle River rapids (4 miles long, falling 49 feet) 858 



Mouth of Kettle river, west of the " Big island " 824 



Foot of Kettle River rapids .* 809 



Mouth of Snake river 798 



At bridge of the Grantsburg*b ranch, Saint Paul and Duluth railroad 775 



At Rush City ferry 770 



Mouth of Sunrise river 758 



Mouth of Trade river 753 



Head of Saint Croix rapids (6 miles long, falling 53 feet) ! . . . . 742 



Mouth of Big Rock creek ^ 726 



Foot of Saint Croix rapids, at the town of Saint Croix Falls 689 



At Taylors Falls, the head of steamboat navigation, three-fourths of a mile 



below the last 687 



At head of Rock island 685 



At Osceola 683 



At bridge of the IMinneapolis, Sault Ste. Marie and Atlantic railway, bed, 



670 ; low and high water 680-697 



Mouth of A pple river 672 



At bridge of the Wisconsin Central railroad, bed, 666; ordinary low stage 



of water, 676 ; extreme low and high water 670-689 



Lake Saint Croix (maximum depth, 25 feet), extreme low and high water, 



667-687 ; ordinary stage 672 



Junction with the Mississippi river at Prescott 667 



Preglacial Rivers in the Saint Croix Valley 



The very long Tertiary era, preceding the Ice age, had permitted the 

 larger streams of Minnesota and Wisconsin to erode deep and wide, well 

 matured valleys, free from waterfalls or strong rapids, and having no 

 narrow, rock-walled gorges, like the Dalles of the Saint Croix. But in 

 the northern, drift covered j)art of the United States, and throughout 

 Canada, the rivers, on their again coming into existence when the ice of 

 the Glacial })eriod melted away, found themselves in many places turned 

 aside from their i)reglacial courses by the drift deposits and by the move- 

 ments of continental uplift and subsidence that were associated with the 

 Ice age. In some cases formerl}'' independent streams were thus united 

 to make a single larger river system ; and often a river was turned out of 

 its old drift-filled valley for a com[)aratively short distance, as a few miles, 

 being there compelled to cut a new gorge in the bed-rocks. 



One or the other of these results of the Glacial period has been well 

 ascertained as the fortune of so many rivers in the great drift-covered 



