^^G PROCEEDINGS OF THE GEOLOGICAL SOCIETY. 



rich veins of galena which traverse the thick beds of superincum- 

 bent raagnesian limestones seem to shrink to insignificance when 

 they reach the thin layers of shell limestone, and they have not 

 hitherto, either in Iowa, Kentucky or Tennessee, been considered 

 worth exploring. 



In Dearborn county, Indiana, I noticed, in this formation, hy- 

 drated brown oxide of iron in considerable masses ; almost the only 

 instance that came under my eye, and how extensive I had not op- 

 portunity to ascertain. 



Dr. Troost informs us that he observed in these rocks, in the 

 vicinity of Nashville, veins of compact and crystallized sulphate of 

 barytes, a beautiful blue sulphate of strontian, together with sulphate 

 of lime. 



Some of the beds afford a marble of considerable beauty, pre- 

 senting sections and markings of organic remains. 



Where these limestones and marls prevail, the soil is rich and 

 productive, furnishing luxuriant pastures. The beautiful farms of 

 Bourbon and Fayette counties, Kentucky, spoken of as the " Garden 

 of the West," are based on this formation. 



No inferior rocks are visible in a N.W. direction until the vi- 

 cinity of the Wisconsin river ; there the blue fossiliferous limestone 

 is found resting conformably on a sandstone, sometimes of a deep 

 red and sometimes of a white colour, and resembling loaf-sugar. Be- 

 neath this succeeds a magnesian limestone so like the lead-bearing 

 rock, both in external appearance and chemical composition, as not 

 to be distinguishable in hand specimens*; it alternates with and 

 rests on sandstones similar to those above it. 



The position of these rocks, in connexion with the previously de- 

 scribed strata, is exhibited on the northern part of the map. 



As I have never found any fossils in these sandstones, and only a 

 few imperfect casts of shells in the magnesian limestone, I am not 

 at present prepared to assign to them their proper place in the geo- 

 logical series. 



To the S.E., beyond the Cumberland mountains, the blue lime- 

 stone rests unconformably on the inferior stratified rocks of East 

 Tennessee. These latter rocks dip south-easterly at a very high 

 angle, in some places almost vertically, but their dip is towards, in- 

 stead of away from, the granitic rocks. It is possibly the case that, 

 since they show themselves in the Sequachee valley between the 

 spurs of the Cumberland mountains, these rocks may have suffered 

 dislocation somewhere in the vicinity of that range of mountains 

 previously to the deposition of the superincumbent strata ; but no 

 hypogene rocks have yet been discovered in that vicinity. That dis- 

 turbances however have taken place on the eastern side of that range, 

 of date subsequent to the deposition of the coal, is certain ; for the 



* It differs however from this rock in several particulars when examined in 

 situ ; it is almost destitute of fossils ; its lower members have sometimes a green- 

 ish tint, and the imbedded siliceous masses are more inigged and quartzose. Beau- 

 tiful crystallized specimens of rose-coloured quartz are of frequent occurrence in 

 its beds, and chert of an oolitic structure is also abundant. 



