328 Tertiary. 



height of 300 feet. Along the Brule river, in the vicinity of the mouth 

 of the Nebagamain, where the river is 300 feet above Lake Superior 

 river terraces are found 30, 80, and 190 feet above the river. From 

 the top of the highest terrace, or level of the surrounding country, to 

 the corresponding top on the opposite side of the valley, the distance 

 is about a mile. 



The lake terraces and lake deposits of sand and clay at these heights 

 in Wisconsin, show that Lake Superior has stood at a height sufficient 

 to have overflowed the highest lands in an}- of the States south of it. 

 The driftless region in the western half of the State, is alike conclusive 

 against anj^ of the drift phenomena in the eastern part, having been 

 the result of glacial action of anj^ kind, and they both unite in testify- 

 ing against a continental ice sheet, or glacial period. 



In Dakota count}', Minnesota, there occurs an outlier of the St. Pe- 

 ter's sandstone, known as '-Lone Rock," owing to its standing in a 

 prairie, and forming a conspicuous object for many miles in all direc- 

 tions. Its summit is about one hundred feet higher than the sur- 

 rounding countr}^ and from this point a number of outliers and pin- 

 nacled rocks of the same sandstone may be seen. One of these is 

 called "Chimne}" Rock," from its fancied resemblance to a chimney; 

 and another, standing seventj' feet high above the surrounding coun- 

 try, is known as " Castle Rock," the upper twent}- feet of which is now so 

 slender that but few centuries will pass before it totters and falls, under 

 the wearing effects of subserial denudation. These sandstone outliers 

 are monuments attesting the erosion which has taken place since Silu- 

 rian times, and yet, in the vallej^s of this count}-, the drift prevails and 

 bowlders abound. In Wabasha count}'^, we have the " Twin Mounds," 

 and in Olmstead count}-, the " Sugar Loaf Mound " and the " Lone 

 Mound," and numerous isolated bluffs, attesting the erosion for the 

 same period. In Fillmore county, the Trenton Group forms precipit- 

 ous bluffs. It rises perpendicularly from the short talus at the base, 

 which adjoins the creek, formiuof canons, which widen as we descend 

 the streams, and which, like the monuments of other counties, attest 

 the erosion through long periods of time. The weathering and erosion 

 have left many scenes in the bluffs of wild and picturesque beauty, as 

 at Weisbeck's dam, in Spring valley, that, standing alone, or consid- 

 ered in their relations to each other, as their bearing is found in all 

 directions of the compass, are convincing proofs of the non-existence 

 of the glacial epoch. But the strongest proof, it seems, that one could 

 wish against the glacial speculation, may be seen in two lonely towers, 



