72 THE GEOLOGY OF MINNESOTA. 



[Nicollet, 1838. 



great numbers to collect it, but to which they now seldom resort, as it is now comparatively 

 scarce at least so I was told by Sleepy Eye, the chief of the Sissitons, who accompanied me 

 during this excursion. 



As I did in the case of the red pipestone described above, I will state the mineralogical 

 character of the Indian blue earth or clay. It is massive, somewhat plastic, emits an argillaceous 

 odor when breathed upon ; color bluish green ; easily scratched with the nail, when formed into 

 hardened balls. The acids have no action upon it ; it is infusible before the blowpipe, but loses 

 its color and becomes brown. This color is due to the peroxide of iron which it contains in the 

 proportion of ten per cent, at least. It contains no potash and but a small proportion of lime. 

 It is a very different mineral from that described by Dr. Thompson under the name of pipe-clay. 



Next comes the region of country between the St. Peter's and the upper portions of La 

 Hontan and Le Sueur rivers, above referred to. This is an extensive district, thickly set in 

 forests amidst which there are reported to be many large lakes. The French give to the forests 

 the name of Bois-francs, or Bois-forts, whenever they are not composed principally of trees 

 belonging to the family of the Coniferce. 



To complete an account of the physical geography of the country, including the Undine 

 region with the last mentioned, I will now enumerate some of the most important trees, shrubs 

 and plants that characterize its sylva and flora. 



The whole country embraced by the lower St. Peter's and the Undine region exceeds any 

 land of the Mississippi above Wisconsin river, as well in the quality and quantity of its timber 

 as the fertility of its soil. The forests of the valley on the right bank are connected by groves and 

 small wooded streams of the adjoining prairies with the forest called Bois francs, and they extend 

 so far southwest as to include the lands of the upper waters of the Mankato river. 



The forest trees, as reported to me by Mr. Geyer, are chiefly soft maple, American and red 

 elm, black walnut, the nettle tree, basswood, red and white ash ; the undergrowth, the common 

 hawthorn, prickly ash, high cranberry, red root, gray dogwood, fox grapes, horse-briar and moon- 

 seed. Among the herbs are the wild and bristly sarsaparilla, Indian turnip, the gay orchis and 

 others; rushes and the flowering ferns are abundant along the low banks of the rivers. The 

 valley prairies are rich in pasture grasses and leguminous and orchideous plants, such as the 

 yellow lady's slipper, American and tufted vetch, and others. The lowest parts near the borders 

 of the woods, and those subject to inundations, are filled with the high weeds common to such 

 places as the ragged cup, tall thistle, great bitterweed, the tuberous sunflower, and others. 



Swamps are frequent, and some of them contain extensive tracts of tamarack pines. Cedars 

 grow, intermixed with red birch, on the rocky declivities of the lower Mankato river. Red and 

 bur oak, with hazel, red-root, peter's-wort, and the wild rose, are the trees and shrubs of the uplands. 

 There are, besides, thickets of the poplar birch that are frequent in the elevated prairies near the 

 river. The prairies are very luxuriant, and generally somewhat level and depressed ; the gum- 

 plant and button snake-root are their most abundant and conspicuous herbs. 



To give animation to the Undine region, and to the valley of the St. Peter's, as well as to 

 develop trade between the British possessions, the territory of Iowa and the state of Missouri, it 

 would be necessary for government to open routes of communication between St. Peter's and the 

 Travese des Sioux, through the Bois francs mentioned above ; between St. Peter's and the Prairie 

 du Chien ; between Dubuque and the Lac-qui-parle ; through the Undine region, with a fork in 

 the direction of the Traverse des Sioux, passing by Fremont* and Ofcomanf lakes, (which latter 

 is at the headwaters of La Hontan river,) and in other directions that would naturally suggest 

 themselves. 



The geological formation that characterizes the Undine region as well as the St. Peter's, 

 as far nearly as the mouth of the Waraju, is the same as that of Fort Snelling which I shall 

 describe further on. It consists mainly in a thick stratum of friable sandstone as the basis, 

 succeeded by a deposit* of limestone, which is sometimes magnesian, and occasionally contains 

 fossils ; the whole covered by what I have called the erratic deposite. 



The sandstone forms the Little rapids of the St. Peter's, and, reappearing at the Traverse 

 des Sioux, determines other rapids that are observed in a beautiful stream! two miles northeast of 



* Probably Clear Lake, near Waseca, 



f Lake Elysian. 



i Moon creek, now called Cherry creek, at Ottawa. 



