238 APPENDIX. 



interesting and someAvhat uncommon feature in the geology 

 of Western America presents itself. I refer to the strata (of 

 considerable depth) which crop out along a narrow strip of 

 the northern boundary-line of this district, and which are 

 chiefly observable in the bluffs on both sides of the Wisconsin 

 River, whence (if we may rely on the representations of 

 Schoolcraft and others) they extend north even to the Falls 

 of St. Anthony. 



" These strata are interesting ; first, as being the only 

 instance known to me, in the Valley of the Missisippi, in 

 which the rocks underlying the blue limestone can be seen 

 emerging from beneath it to the surface ; and, secondly, as 

 apparently supplying an example of those alternations of 

 neighboring strata, to which I have already alluded as being 

 partial exceptions to the invariable order of geological super- 

 position. 



*' Immediately below the substratum of blue limestone 

 which constitutes the lowest member of the moiutitain lime- 

 stone group, where it has been observed east of the Missi- 

 sippi, there occurs, and shows itself in the Wisconsin bluffs, 

 a stratum of sandstone, in some places of a deep red, and in 

 others of a white color, resembling loaf-sugar ; and thence 

 called, in Dr. Locke's diagrams exhibiting the sections on 

 the Wisconsin River, saccharoid (or sugar-like) sandstone. 



" Immediately beneath this succeeds a magnesian lime- 

 stone, so similar to the cliff limestone, both in external appear- 

 ance and chemical composition, as not to be distinguishable 

 from it in hand-specimens, alternating with other layers of 

 sandstone, similar to that above-described. 



" The actual average dip of the rocks throughout the dis- 

 trict, according to the observations made by Dr. Locke, is 

 from nine to ten feet per mile, but it is occasionally much 

 greater. For example, from the mouth of Turkey river to 



