LAKES TRAVERSE, BIG STONE, AND LAC QUI PARLE. 19 



thrown across the valley. He also showed that Lake Pepin, on the 

 Mississippi, is dammed in the same way by-tte sediment of the Chippewa 

 River; and that Lake St. Croix and the last 30 miles of the Minnesota 

 River are similarly held as level backwater by the recent deposits of the 

 Mississippi. 



The valleys of the Pomme de Terre and Chippewa rivers, 75 to 100 

 feet deep along most of their course and one-fourth of a mile to 1 mile 

 in width, were probably avenues of di-ainage from the melting ice fields 

 in their northward retreat. Between these rivers, in the 22 miles from 

 Appleton to Montevideo, the glacial floods at first flowed in several 

 channels, which are excavated 40 to 80 feet below the general level of the 

 drift sheet, and vary from an eighth to a half of a mile in width. One of 

 these, starting from the bend of the Pomme de Terre River, 1^ miles east 

 of Appleton, extends 15 miles southeast to the Chippewa River, near the 

 center of Tunsburg. This old channel is joined at Milan station by 

 another, which branches oft" from the Minnesota Valley, running 4 miles 

 east-southeast; it is also joined at the northwest corner of Tunsburg by a 

 very notable channel which extends eastward from the middle of Lac qui 

 Parle. The latter channel, and its continuation in the old Pomme de Terre 

 Valley to the Chippewa River, are excavated nearly as deep as the channel 

 occupied by the Minnesota River. Its west portion holds a marsh generally 

 known as the "Big Slough." Lac qui Parle would have to be raised only 

 a few feet to tm-n it through this deserted valley. The only other localities 

 where we have proof that the floods of the River Warren at first ran in 

 several channels are 7 and 10 miles below Big Stone Lake, where isolated 

 remnants of the general sheet of till occur south of Odessa station and 

 again 3 miles southeast. Each of these former islands is about a mile long, 

 and rises 75 feet above the sun-ounding lowland, or nearly as high as the 

 bluffs inclosing the valley, which here measures 4 miles across, having a 

 greater width than at any other point. 



THE RED RIVEE VALLEY. 



Proceeding northward to the area of Lake Agassiz, whose outflow 

 foi-med this channel, the observer finds that the broad watercourse, with 

 its bluffs and the adjoining highland on each side, ends a few miles north 



