203 



Dr. C. T. Jackson exhibited specimens of the following 

 minerals, which he had obtained during his recent explo- 

 rations on Keweenan Point, Lake Superior : 



Datholite, from a large vein in trap rocks, in large and brilliant 

 crystals, having a violet tint near their edges, owing to the presence 

 of oxide of manganese. The crystals of this mineral also fre- 

 quently contain delicate scales of brilliant metallic copper enclosed 

 within them. Prehnite, which also abounds in large veins in the 

 trap rocks of the same region, contains metallic copper in the 

 midst of the crystals. 



This metal is also found in calcareous spar, and in nearly all 

 the veins which traverse the amygdaloidal trap, and the contiguous 

 conglomerate rocks. 



A few specimens of native copper and silver, from a vein in the 

 amygdaloid of Eagle river, were exhibited, and it was remarked 

 that the copper, besides containing a certain proportion of silver 

 combined with it in the state of an alloy, had a number of patches 

 of pure silver intermixed with it, appearing as if it had been seg- 

 regated from the alloy during its cooling from a melted state. 

 It not unfrequently happens, that pieces of copper and silver are 

 united only at their edges by interfusion, without being alloyed be- 

 yond those limits. Sometimes small veins of the silver traverse 

 masses of solid metallic copper. In one piece it was observed, 

 that at one end of a piece of copper the silver was in separate 

 patches and veins, and at the other the metals were combined as 

 an alloy. It is difficult to explain these singular phenomena, and 

 chemical art has not succeeded in imitating them ; for when silver 

 and copper are melted together, they intimately unite, and the sil- 

 ver disappears from view. There can be no doubt, however, that 

 the metals found in the Lake Superior amygdaloidal trap, have 

 been fused at as high a temperature as was required to liquify the 

 rocks in which they are found, for they bear evident marks of en- 

 tire fusion, and are as vesicular as the common lavas of Vesuvius, 

 Etna, and Peak of TenerifTe. 



At some future meetings, a more full account of the mines of 

 Lake Superior may be laid before the Society. 



Dr. Storer announced that he had received the following 

 Fishes, from Mobile Bay, from Geo. W. Abbot, Esq., viz. : 



