PLATE XXXIX. 



SWIFT AND CHIPPEWA COUNTIES, 1888. WARREN UPHAM. 



These counties are but little more diversified than Renville and McLeod counties. 

 They have the same general prairie surface, based on the uniform till sheet. Still, in 

 the towns of Hegbert, Camp Lake, Kirkhoven, Appleton and New Posen, in Swift 

 county, and in Kragero, Chippewa county, the surface is rolling and morainic. Along 

 the Pomme de Terre river in Shible, Moyer and Appleton is a tract of drift gravel, 

 nearly level, lying fifty feet below the general surface of the drift sheet, and rising 

 from twenty-five to forty feet above the Pomme de Terre. A similar flat grav- 

 elly area extends several miles about Benson, lying ten to twenty feet above the Chip- 

 pewa river. A terrace extends along the northeast side of the Minnesota river from 

 Myers nearly to Montevideo, elevated twenty-five to forty feet above the river. Its 

 greatest width is about half a mile, in section 29, Sparta. 



The older till surface is plainly evinced in several places in Swift county, about 

 Appleton, and westward into Big Stone county and southward to Lac qui Parler It 

 here has the character, not of an ancient soil with vegetation, but of a stony layer 

 from which all soil had been removed prior to the overspreading of the later till. 

 These boulders are closely compacted in till, and they seem not to have been moved, 

 but overridden, by the latest ice-sheet, since they are glaciated in the direction in 

 which the ice-sheet is known to have moved in this part of the state. The intergla- 

 cial soil must have been removed by water perhaps by the copious drainage that 

 resulted from the last glacial epoch during the period of its oncoming. As the cold 

 increased, the boulders were held in place by the frozen condition of the earlier till, 

 and were subsequently buried under the later ice and its till sheet. 



Very interesting abandoned channels of older drainage occur between the Pomme 



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de Terre and the Chippewa. It appears that the Pomme de Terre and the Minnesota 

 rivers cooperated formerly, when swollen by glacial drainage, in the formation of 

 three islands elongated northwest and southeast, and it is probable that this division 

 of the river was necessitated by the obstruction caused by the great size and abun- 

 dance of boulders that here accompany the valley, resulting from the disintegration 

 of the stony older till. Such division and expansion of the present rivers, by reason 

 of abundant boulders, is a common feature in the counties further north. 



Outcrops of the usual granite and gneiss are frequent along the Minnesota valley, 

 the most important being at Granite Falls and Minnesota Falls, - N. H. w. 



