HISTORICAL SKETCH. 103 



1871, Kloos.] 



tain higher formations, such as the Iowa Subcarboniferous formation, but 

 in the absence of exposures of the rock nothing could be ascertained with- 

 out artificial excavations. 



The discussion of the " Tertiary phenomena " by Mr. Hurlbut embraces 

 Prof. J. D. Whitney's view of the origin of the driftless area in Iowa, and 

 the opinions of Gen. G. K. Warren concerning the former direction of drain- 

 age of the Minnesota and upper Mississippi "westward into the Cretaceous 

 ocean," in which he groups in a new and interesting manner many topo- 

 graphic and hypsometric facts, going to show that the interior of the state 

 is a basin whose greatest depression is along the valley of the Minnesota, 

 from its source to the head of lake Pepin. " The supposed surface and shore 

 line of this lake basin is very well indicated, in many places, at about one 

 thousand feet elevation above the sea, by clay terraces and bluffs, containing 

 trunks and branches of trees, lignite clay and other lacustrine formations." 



KLOOS' GEOLOGICAL OBSERVATIONS IN MINNESOTA. 



In the same journal, in 1871. Mr. J. H. Kloos of St. Paul, records sundry 

 geological observations made in the northern part of the state. He sketches 

 the country briefly along the line of the new railroad from lake Superior to 

 the Mississippi river at St. Paul, noting most closely the region of the slates 

 on the St. Louis river, which he assigns to the Huronian formation ; the 

 conglomerates and red sandstones he assigns to the Potsdam, the latter being 

 unconformable on the former, with a dip six or seven degrees toward the 

 south ; and suggests that beds of iron ore underlie the slates of the St. Louis 

 river, as they do the slates of the Marquette iron range in Michigan ; the 

 huematitic and magnetic iron ore at Vermilion lake being perhaps in that 

 horizon, and thus the lowest member of the Huronian formation. 



In respect to the rocks at Duluth he describes, in general terms, the 

 " Duluth granite," as a coarse crystalline rock consisting principally of a 

 grayish-white feldspar showing three distinct cleavage planes, two of them 

 being nearly at right angles ; one plane has a glassy lustre, and the other a 

 brilliant pearly lustre, with striae which he regards as an indication of 

 labradorite. Another constituent he named diallage, or hypersthene ; and 

 another magnetic iron. The rock he pronounces hyperyte, provisionally. 

 He mentions the first rocks forming the immediate shore at Duluth, styling 



