58 Notes OH the Local (Teohxjij of Manhato — Bechdolt, 



est points of the Leaf hills, 1,(500 to about J, 750; of the Coteau 

 des Prairies, 1,800 to about 1,960; lake Traverse, 970, and Big 

 Stone lake 962; hike Benton, 1,754; lake Shetek about 1,475; 

 Heron lake, i,40;J; Mille Lacs, 1,251, and lake Minnetonka, 928. 



The average elevation of the whole state cannot be lest than 

 1,200 feet, which is )J70 feet above the plain of modified drift on 

 which Minneapolis is built; and it may be found, when carefully 

 estimated throughout, even as high as a quarter of a mile, 1,320 

 feet above the sea. This is about half the average altitude of the- 

 whole United States, which is aj)proximately 2,600 feet above the 

 sea; .but probably no state east of the Mississippi river has a greater 

 mean altitude than Minnesota. Humboldt estimated the mean 

 height of all North America to be 1,500 feet, and of Knrope. 1,340 

 feet. 



\ Fa])er (i. | 



NOTES ON TifK LOCAL GEOLOGY OF MAxXKATO. A PRE-GLAC.IAL KIVKK 

 (CHANNEL.- ,1. F. Bpchc/olf. 



What is locally known as Yan Brunt's Slough lies in the west- 

 ern part of the city of Mankato, opens on the flood plain of the 

 Minnesota river, and has a devious course in a direction slightly 

 west of south. 



The sides of the Slough resemble the banks of a river rather 

 than those of a lake. Tn all their windings the opposite shores 

 remain parallel. 



This feature holds true for the entire length of the Slough 

 except at ojie point where the concave side is not concentric with 

 the opposite bank but makes a noticeable bay. This want of uni- 

 formity will be explained a little farther on. South of th^ point 

 referred to lies Indian lake, an oblong pond, gradually filling up 

 with silt. The depression of the Slough, above the head of the 

 lake, turns to the west, along a small affluent of the lake, which is 

 usually dry in mid-summer, to its source in a swamp. From this 

 swamp another small stream Hows west along the depression 

 emptying into the Le Sueur river, not over one-fourth mile above 

 the railroad bridge. Chalk run, as this stream is called, at its 

 source, the highest place in the Slough depression, is probably not 

 over twenty feet above low water in the Le Sueur. The outlet of 

 Indian lake runs north along the slough, loses itself in the swamp.. 



