162 QUARTERLY JOURNAL. 



And in a ton of the ore as delivered at Boston, there is $568i 

 worth of silver and over $200 worth of copper; so that it is morei 

 properly a silver mine than a copper mine; 17 lbs. 9 oz ot thei 

 clean metal was obtained from 50 lbs. of the ore, by careful assay:, 

 50 lbs. of copper ore gave 11 lbs. 4 oz. in large pieces of copper 

 and silver, besides the washings; and an assay of that yielded 663 

 grains of pure silver, or equal to 25.2 of silver to a ton oi 



Dr J also stated his observations on temperature. On Laki 

 Superior, in August, the air was 53.8 Faht^at noon; the water 

 was 48.2 Faht. in lat. 47 deg. North. On Lake Huron Juli 

 23d the air was 66.5 Faht. noon; and the water was 68 1 aht. 

 both observations taken while the winds were blowmg prettji 



fresh 



Prof Shepard expressed great doubts whether the copper re 



gion of Lake Superior would not be a failure after all. He thoughl 



it was a formation analogous to the new red sandstone of theOoB 



npcticut valley. Copper was found in numerous places along thj 



valley, diffused through quartz and barytes spar, and entangle 



with trap at the contact surface of the primary and secondarj 



rocks. It was found thus chiefly on the western frontier line ( 



the secondary; at Rocky Hill near Hartford, and at Enfield Falli 



Here was found native copper, red oxide and black oxide ot coji 



per, copper pyrites, &c.; all washed down from their original m^ 



trix into the valley, and washed into the crevices of the sandstone 



He conceived this valley to have been once a lake, at the bottoi 



of which were large masses, sheets and boulders of copper. ThJ 



came the trap dykes fusing up to the surface, and brought up tF^ 



copper, through which they passed, the copper resting on bo 



sides of the trap as at Mount Carmel. He conceived Lake bup^ 



rior to have been originally a primitive formation; the new rf 



sandstone was found on either side of the Lake; and the eoppj 



found there was swept by waters into the vertical chinks ot tJ 



sandstone; then as the trap came through it melted the copper OD 



producing results analogous to those in the Connecticut val e 



and thus he concluded that the Lake Superior copper ore is merely 



superficial formation reduced from copper ores pre-existing in t! 



sandstone. The presence of silver could also be accounted for; 



the great copper regions of Germany which exists from the cos 



of the Elbe to the banks of the Rhine, in the rich copper mu 



wrouP-ht near Rottengen in 2,000 tons of copper there were foui 



20,000 marks of silver, or equivalent to 10,000 lbs. weights 



Dr* Jackson said he had doubts before he went up to Lai 

 Superior, but he is now satisfied the copper ores there could n 

 have been reduced from sulphurets by the action of trap dykt 



