PLATES (PAGES) XXIII AND XXIV. 



PlPESTONE AND ROCK COUNTIES, 1884. N. H. WlNCHELL. 



These counties, lying outside of the moraine of the coteau, are still covered with 

 a sheet of till, but this till presents some peculiarities. It has the aspect of greater 

 age, i. e., the boulders are rotted, and many of the pebbles, especially of the lime- 

 stone, though maintaining their forms in the clay, are largely in the condition of a 

 white residuum which crumbles easily. The channels cut by the streams are deep, 

 and appear to have been excavated primarily in interglacial or pre-glacial time. In 

 these counties are seen occasional large granite boulders like those which pertain, 

 in counties further east, to the older drift-sheet. Some of these are remarkable for 

 size. The six granite boulders that originally lay on the red quartzyte surface near 

 the pipestone quarry were evidently once united in one mass, being of the same kind 

 of rock, and together they constituted the largest known ice-transported block in 

 Minnesota, making a mass fifty to sixty feet in diameter. 



The surface of these counties is generally smooth or gently undulating; but in 

 the northeastern corner of Pipestone county the contour is very rough, being crossed 

 by the crest of the Coteau des Prairies. Here the hills are abrupt, and often very 

 stony, and rise from 100 to 150 feet above the valleys. There are patches of some- 

 what broken and morainic character further south, as in Spring Water and Elmer, 

 and in Denver, but they cannot be traced to any connection with a morainic origin. 

 They are rather to be attributed to the action of abundant drainage from the ice of 

 the earlier glacial epoch, concentrated locally so as to carry away the finer part of 

 the till, leaving mainly gravel and sand. 



There is a modified drift, of a loamy character, covering the southern part of 

 Rock county, in which are found no boulders. This is believed to be a northward 

 extension of the loam of the Missouri valley, and is comparable with that seen in 

 Goodhue county. 



The Potsdam quartzyte, which probably underlies all of Pipestone county and 

 the northern half of Rock, affords some small surfaces of bare rock, the principal 

 one being known as " the mound," two or three miles north of Luverne. This rock 

 also contains the layer of hardened red clay known as catlinyte, from which the 

 Indians have long made their peace-pipes. The locality from which it is quarried is 

 near Pipestone city, within a small "Indian reservation." In this catlinyte have 

 been found two fossil species, viz., Paradoxides barber i and Linyula calumet, indicating 



