F 



r 



234 ATofice of Messrs. Foster and Whiifiey^s Report 



lent of the Potsdam sandstone. The following are their observa- 

 tions on this point. — p. 117. 



" The sandstone, as we ascend from the lower strata to the 

 higher, is found to be less colored by the oxyds of iron, and to 

 take into its composition particles of lime, until finally it passes 

 into well characterizedj compact, magnesian limestone. The 

 upper portions of the sandstone effervesce with acids, where a H 



granular structure only is recognizable by [he eye. We apply 

 the term magnesian to this belt to define its lithological charac- 

 ters, although the associated organic remains would §eem to in- 

 dicate the presence of several of the lower Silurian groups, 

 which cannot be recognized by lithological differences. 



The whole of the northern slope of the anticlinal axis bears 

 evident marks of having been subjected to extensive denudation ; 

 and hence over the greater portion of this region we look in vain 

 for traces of limestone rocks. If they existed, they have been 

 swept away ; and wherever we penetrate through the thick de- 

 posit of clay and sand, we find the rock in place to be sandstone. 

 A limited patch of limestone, however, yet remains west of 

 L'Anse, forming the highest elevation in that direction till we 

 reach the trap range. It is in township 51, range 35, and occu- 

 pies a portion of four sections. It was first discovered by Mr. 

 C. 0. Douglass, in the summer of 1846, but nothing farther was 

 known until the township was subdivided in 184S, when its ex- 

 tent and exact locality were determined. 



Near the quarter-post, between sections 13 and 14, township 

 51, range 35, the limestone is seen in place, forming a bluff, 

 about 50 feet above a small stream at its base. Here the strata 

 are nearly horizontal, though large blocks have slidden down the 

 side of the hill, and thus appear to dip towards the east. The 

 limestone rests upon a white sandstone, which belongs to the up- 

 per part of the formation which we have described as underly- 

 ing the whole of this valley. 



A little to the west of the line, between sections 23 and 34, 

 and extending for a little more than a mile, the limestone is seen 

 in a high cliff which runs south and gradually bends to the east- 

 ward, crossing the line, in several ridges, near the southern limit 

 of these sections, when it disappears beneath the drift materials. 

 Ledges of rock are occasionally exposed, from 20 to 50 feel in 

 thickness. The height of the bluff above the surrounding coun- 

 try is fully 200 feet; and about 600 feet above Lake Superior. 

 The limestone is distinctly stratified, in layers from an inch to a 

 foot in thickness, which dip, according to measurements taken 



o 



7 



along the lower edge of the precipitous portion, from 25^ to 30 

 and the direction of the dip is always to the eastward^ varying 

 at different points from N. 50^ E. to S. 20^ E. 



