292 APPENDIX. 



Latitude of camp near Point aux Salles, Lake 



Michigan, Sept. 5 44° 5' 17' 



Latitude of camp at Grand Traverse Bay, Lake 



Michigan, Sept. 7 45 34 24 



3. MINERALOGY AND GEOLOGY. 

 VI. 



Report on the Copper Mines of Lake Superior. By Henry E. 

 Schoolcraft. 



To the Hon. John C. Calhoun, Secretary of War. 



Vernon (Oneida County, N. Y.), November 6, 1820. 



Sir: I have now the honor to submit such observations as 

 have occurred to me, during the recent expedition under Gov. 

 Cass, in relation to the copper mines on Lake Superior; reserv- 

 t/'ing, as the subject of a future communication, the facts I have 

 collected on the mineralogy and geology of the country explored 

 generally. 



The first striking change in the mineral aspect of the country 

 north of Lake Huron, is presented near the head of the Island of 

 St. Joseph, in the Eiver St. Mary, where the calcareous strata of 

 secondary rocks are succeeded by a formation of red sandstone, 

 which extends northward to the head of that river at Point Iro- 

 quois, producing the falls called the Sault de Ste. Marie, fifteen 

 miles below; and thence stretching northwest, along the whole 

 southern shore of Lake Superior, with the interruptions noted, to 

 Pond du Lac. 



This extensive stratum is perforated at various points by up- 

 heaved masses of sienitic granite and trap, which appear in ele- 

 vated points on the margin of the lake at Dead Eiver, Keweena 

 Point, Presque Isle, and the Chegoimagon Mountains. It is 

 overlaid, in other parts, by a stratum of gray or neutral-colored 

 sandstone, of uncommon thickness, which appears in various 

 promontories along the shore, and, at the distance of ninety miles 

 from Point Iroquois, constitutes a lofty perpendicular and ca- 

 verned wall, upon the water's edge, called the Pictured Eocks. 



