60S THE GEOLOGY OF MINNESOTA. 



[Bridge water kame. 



lake-like river, than a narrow rapid river required for this kame, it could 

 not have been produced at the date when the Cannon first received the 

 Minnesota; and again, 



8. It could not have been produced by the Cannon when the Minne- 

 sota acquired its lower passage to the Cannon, forming its lower gravel 

 terrace, since at that time the ice would have been withdrawn from the 

 region in which it lies. 



9. It must, hence, have been produced by the waters of the Straight 

 river alone. 



10. As there is evidence of the obstruction of the Straight river by 

 the glacier south of Faribault, causing the discharge of the Straight river 

 through the north branch of the Zumbro, it must have been produced at a 

 later date, when the ice had shrunken so as to allow of the drainage of the 

 Straight river toward the north. 



11. Hence the lake that covered the upper portions of the Straight 

 river valley was lowered to the level of the top of the ice. 



12. The river flowed over the margin of the glacier, and presumably 

 at first on its very surface. 



13. As the river received the gravel from the glacier, the gravel must 

 have been at the same level, or above it. 



14. As the gravel is the result of washing of the till and the removal 

 of the clay, the till itself must have been as high or higher than the surface 

 of the river. 



15. The till was therefore on the surface of the ice. 



16. The kame was not formed by a sub-glacial stream butjjy an epi- 

 glacial stream. This results from the foregoing conclusions, and also from 

 the fact that the bottom of the kame actually rises about 75 feet at the 

 point where it leaves the flood-plain on sec. 5, and ascends to the S.W. | of 

 sec. 33, where it lies on red till, the latter point being about three-quarters 

 of a mile north of the former. 



17. The ice bearing the gray till was projected eastward over the pre- 

 existing sheet of red till, without entirely disrupting and removing the red 

 till, at least where the red till lies on the St. Peter sandstone. At higher 

 levels, over the Trenton limestone in sec. 33, Bridgewater, the red till is not 

 found between the gray till and the rock. 



