241 



persistent along the copper range to the eastward in Michigan. It is 

 visible in about the same relation to the conglomerate, at the Black, 

 Iron and Ontonagon Rivers. At Black and Presque Isle Rivers I have 

 noticed specks of carbonate of copper, disseminated, as in the Mans- 

 felt slate. But one analysis has been made of this rock (formation 1, 

 6), which is as follows : — 



Specific gravity, 2,690. Color of powder, bluish gray. 



Silex 75.60 



Protoxide of Iron 14.00 



Manganese 0.35 



Alumina 7.30 



Lime 0.95 



Magnesia 0.95 



Carbonaceous matter, moisture and loss 1.05 



100.00 



In the belts of sandstone that alternate with trap, it is common to 

 find native copper, out of the veins, disseminated in fine particles, 

 crystals and spangles, in some places sufficient to pay for stamping 

 and working the rock. 



The analyses here given were made for the Wisconsin Survey by 

 Professor J. L. Cassells, of the Cleveland Medical College. 



Of formation 4, with the exception of specimens containing a large 

 per cent, of iron and regarded as ores, only two were analyzed. 

 This is a black fine-grained slate, with a silicious aspect, and dark 

 gray powder. It was taken from near the iron belt above it, at a 

 locality 3 miles southwest of the trail, and about 12 miles from Lake 

 Superior. ^^ 



1. Specific gravity, 3,049. ^'^S 



Carbonaceous matter and moisture 1.55 



Silex 80.00 



Protoxide of Iron 1 7.60 



Oxide of Manganese 0.35 



Alumina 0.25 



Magnesia 0.25 



100.00 



2. Compact, tough blue slate. T. 45, N. R. 1 East. Specific 

 gravity, 2,740. 



Moisture and loss 1.25 



Silex 89.60 



Protoxide of Iron 3.60 



Oxide of Manganese 0.22 



Alumina 2.40 



PEOCEEDINGS B. S. N. H,— VOL. IX- 16 DECEMBER, 1863' 



