PIPESTONE AND KOCK COUNTIES. 547 



Boulders. Glacier-marks.] 



In traveling over the plateau of quartzyte, about on section 16, Mound, a large, solitary 

 granite boulder may be seen. It lies directly on the quartzyte. It is rough and granulated, and 

 there is a circular excavation or concavity in the soil in which it lies. It is about ten feet long 

 and five feet high, and has a groove horizontally circumscribing it about a foot in width and three 

 or four inches deep. Taken altogether it immediately reminds the beholder, not less by its gen- 

 eral shape than by this groove, of the artificial stone hammers sometimes found. Its size precludes 

 its being one, but its shape is very like them. The groove may have been formed by the action of 

 ice and water on its sides, as the rock has the appearance of lying, in ordinary seasons, in a little 

 lake of water, which at the time of this examination was entirely dried up. This boulder, like 

 the "three maidens," at the pipestone quarry, must be referred to the date of the earlier boulder- 

 clay. 



On the south slope of one of the drift hills mentioned in the vicinity of the line between 

 Eden and Elmer, about two rods east of the road as it is now traveled, is a boulder of reddish 

 granite, ten feet long and six feet wide. The earth all around this boulder, to a distance of ten 

 or twelve feet, is hollowed out one to one and a half feet below the general level. This is an 

 unusually large block, its hight now projecting being five feet. Smaller boulders, three to six feet 

 in diameter, are seen quite frequently upon the vast prairie of southwestern Minnesota, similarly 

 surrounded by a hollow. These depressions may have been started by the pawing and tramping 

 of buffaloes, the pulverized earth having been then blown away by the winds. The ruts of roads 

 on the prairies seem often to be deepened in a similar way by the winds blowing dust from them; 

 and in winter the wind maintains similar circular depressions about solitary trees, when the sur- 

 rounding country may be covered with two or three feet of snow. 



It has already been mentioned that there are but few boulders in Eock county. They 

 are generally confined to the creek bluffs and valleys. Even on the plateau caused by the red 

 quartzyte running from near Luverne northwestward they are not seen, or are so rare as to be 

 noteworthy for their absence. This is an anomaly, and can be accounted for by the great lateral 

 extent of the quartzyte plateau, so that not many fissures were produced by it in the ice-sheet, 

 where running water could find passage. There would be no place, ordinarily, where foreign 

 boulders would be found, in a drift-covered country, more thickly than on such rocky elevations. 



Glacier-marks. There is evidence of glacier-action, or what has been 

 recognized as evidence of glacier-action, in Kock county south of the Coteau. 

 The quartzyte is polished, striated and sculptured superficially on the tops 

 of the ridges in the central part of the county as only glacier-ice is known 

 to do. At the pipestone quarry (near "the three maidens"), such marks 

 ran 32 W. of S. (true meridian). On the strike of the ledge at the same 

 place they run N. and S., varying to 30 W. of S.* On section 13, Eden, 

 they run in two directions, one direction being about S. 10 W., and the 

 other S. 42 E., within the valley of a little stream. On the rock near 

 the top of the southern side of this valley, which is a shallow depression, 

 glacial marks run S. 32 W. This is but a few rods from the last observa- 

 tion above. At another point, about ten miles north of Luverne, glacial 

 marks were observed running S. 10 W. On the rock at "the mound" they 

 run 25 to 30 and 35 W. In many places they are conspicuous and 

 abundant, and perfectly preserved, covering considerable areas. 



*Allowing ten degrees for the variation of the needle to (he east of the true north. Mr. Upham records glacial 

 marks at the three maidens, and on the N. and S. ledge, both 25 W. of S. 



