INDEX. 167 



Page. 



Prairie du Chien, geology of - 125 



Primary rocks, application of the term - -25 



R. 



Red sandstone group, deficient in the United States - -51 



Rocks, chemical nature of - 26 



Mechanical nature of 26 



Appearance of, changed by ignigenous bodies - 27 



Earliest fossiliferous - 32 



Cause of their inclination 40 



Deceptive stratification of . 41 



Unconformable - 42 



S. 



Salt, below the coal measures in the United States -. - 92 



Saliferous strata in the United States . 115 



Near Abingdon, Virginia - 116 

 Secondary beds, those not reached by tide-water lie west of the Alle- 



ghany ridges - - 43 



Fossil plants of . . . - 88 



Sedimentary rocks, origin of - . - . * 18 



Serpentine . . . 30 



Overlying sedimentary limestone - - 31 



Silurian system, new arrangement of, by Mr. Murchison -. . , &amp;gt; 26 



Explanation of - ... 33 



Origin of the term - - .&quot;,.. . 34 



Equivalent of the grauwacke beds - - 35 



Valley of the Potomac , . . . 42 



Do. do. . 101 



At Flintstone, Maryland - . 103 



Sioux, origin of the term ., . . 128 



Slate, mica . . . . . 28 



Talcose - t - - - 29 



Micaceous, Potomac . . 95 



Springy land, cause of - ..,. . . ,-. g 



St. Peter s river - . . . . 135 



Indian name and course N .... - ; - . f . .. 137 



Passes through Bois Franc - . 139 



Limestone in place - . 140 



Change of mineral formation - . . 145 



Granite in place - . 147 



Grand Portage and laminated rock - . . . 149 



Its sources - .... . 153 



