On the Copper Range of Lake Superior. 115 



is much broken up and fissured by cross-courses at the places 

 opened. 



The metalliferous occurrences yet opened comprise three belts 

 of amygdaloid trap, containing much chlorite, and about two 

 per cent, or upwards of 600 lbs. of ingot copper to the cubic 

 fathom. The conglomerate limiting the series on the west con- 

 tains no copper. 



Soulk Side Zone, — We have given this name to the rocks rest- 

 ing on the Hancock formation from the fact that their characters 

 have been almost entirely developed by the explorations on the 

 lands of the South Side Mining Company. These rocks com- 

 prise a width of over 2100 feet, and are made up of frequent 

 alternations of porous and highly amygdaloidal traps, with belts 

 of sandstone and conglomerates, for a distance of nearly 1000 

 feet, the balance being almost entirely sandstone and conglomer- 

 ate, with an occasional intercalation of a porous trap bed. This 

 zone appears to be almost entirely destitute of metalliferous oc- 

 currences. Beyond its limits the" few explorations made show 

 the rocks to be entirely sandstone, with a constantly decreasing 

 angle of dip, as the igneous rocks are receeded from, till at a 

 distance of two miles it is found in horizontal layers. 



The base of the range, as developed at the southeast limit at 

 [ortapre Lake, is a fissile chlorite rock, the same as forms the 

 J^JiS of the Bohemian or Sulphuret Range at Point Keweenaw. 

 ihis has elevated the bed of trap which rests on it to the north- 

 ^■^st, and the sandstone which lays on it to the southeast, to a 

 considerable angle, amounting, in the case of the trappean rocks, 

 to '0^ but which we have shown becomes gradually less in the 

 northwestern development of these rocks. The decrease in the 

 ^^?ie of dip of the sandstone at the southeast is much more 

 ^5"d than that of the trappean rocks and sandstones, and at a 

 ^■^i^^ance of three quarters of a mile from this line of elevation 

 '' ;';;'nd again in a horizontal position. 



I :ic occurrence of this chlorite rock in proximity to those 

 '"'" of rock which form the base of the Isle Royale series, and 

 J^-^^-tam sulphids and arsenids of copper, would appear to point 

 J^ ^lie identity of the rocks of this zone with those forming the 

 ^O'Uhorn limit of the greenstone or north range, and the north- 

 ^''' ^^-'undary of the southern or Bohemian range of Keweenaw 

 ' ' ' This view is further strengthened by some examinations 



■ made by Samuel W. Hill, Esq., in that region where that 

 in found an extensive series of trappean beds, highly 



■ in composition, and carrying native copper, intercalated 

 ■'H^r beds containing the ores of that metal. There are 



^'y'ibtless many rocks occurrino- in the Bohemian Range, in the 

 Jicmuy of Lac la Belle, porphyritic in character, which are not 

 ^^^eloped in the Portage Lake District, but this does not affect 



