GEOLOGICAL EXPLORATIONS AND LITEKATUKE— 1855. 35 



" at intervals in a belt of slates from G to 25 miles wide, extending for a 

 distance of 160 miles or more westward into the State of Wisconsin." 



ScHOOLCKAPT, Henry R. Observations on the mineralogy and geology of 

 the country embracing the sources of the Mississippi River and the Great Lake 

 basins. Summary narrative of an exploring expedition to the sources of the 

 Mississippi River in 1820. Philadelphia, 1855. Pages 303-362. 



Hemy R. Schoolcraft, as geologist to the expedition of 1820 to the 

 som-ces of the Mississippi, made a report to the Hon. John C. Calhoun, 

 then Secretary of War, giving a brief account of the geology of the region 

 traversed by the exploring party thirty-five years before. In this we find 

 several references to the country with which we are now concerned. The 

 sandstone near Presque Isle and at Granite Point is described as horizontal. 

 The first-named point was recognized as "a headland of serpentine, resting 

 against which is a curious formation of magnesian breccia" (pp. 321-322). 

 Magnetic oxide of iron is reported as occurring in mountain masses in the 

 valley of the Carp River. 



Whitney, J. D. On the occurrence of the ores of iron in the Azoic system. 

 Proc. Am. Ass. Adv. Sci., Vol. IX, 1856, pages 209-216. 



After the ijublication of the "Report," Whitney spent portions of two 

 seasons in the Lake Superior region, and visited the iron districts of 

 Missouri and northern New York. The author finds a strong analogy 

 existing between the relations of the ores with the rocks associated with 

 them in these two districts and in Scandinavia and the relations of the 

 Marquette ores with their associated rock-s. All the facts observed con- 

 firm him in the belief that the Lake Superior ores are Azoic. They 

 Qccur in large quantities, and consist almost uniformly of specular and 

 magnetic oxides. Hydrous ores, carbonates, etc., were not seen in the 

 district, though it is tliought possible that they may exist on the borders of 

 the ore deposits, where they may have been aftected by the adjacent rocks. 

 The larger deposits are described as lacking the characteristics of A^eius. 



