14 THE CANADIAN NATURALIST. [Feb. 



line minerals occur, in which quartz generally preponderates, asso- 

 ciated with calcspar, prehnite and native copper. Some specks of 

 native silver sometimes occur in this veinstone. The strike of the 

 bed is N. 30° E., and the dip about 52° north-westward. 



Between the Grand Portage and Isle Royale Yeins the trap is 

 of the usual character, reddish-grey coloured, with dark-green 

 grains and spots of delessite impregnating it. 



The cupriferous bed of the Isle Royale mine is often of a dark- 

 chocolate colour similar to that of the Pewabic lode. In other 

 places it has the character of the Portage lode, being light-green 

 coloured, non-crystalline and with an uneven fracture, but it is 

 comparatively free from amygdules. 



Trap, as usual, underlies the Isle Royale Yein, and, with other 

 rocks, fills up the space between it and M abb's vein which lies 

 about a mile to the south-eastward. One of these is a conglome- 

 rate resembling that of the Albany and Boston mine, so far as the 

 nature of the pebbles is concerned. The matrix is very porous, 

 and in coarse grains, which are in places cemented together by 

 quartz as well as calcspar. 



Mabb's Vein, upon which mining has also been commenced by 

 the Isle Royale Co., has a matrix of a much more crystalline cha- 

 racter than any of the cupriferous beds already described. It is 

 of a dark-green colour, and is impregnated with grains and irre- 

 gular spots (but not amygdules) of quartz, which is accompanied 

 by epidote and metallic copper. Sometimes, however, an approach 

 to the light-green earthy rock of the Isle Royale vein is noticeable. 



A short distance to the east of Mabb's vein another conglome- 

 rate bed is found. The pebbles are porphyritic here also, but con- 

 tain crystals of quartz as well as of felspar, and the paste is diffi- 

 cultly fusible before the blow-pipe, fine splinters of it only becoming 

 glazed. The pebbles do not seem to be so well rounded as in the 

 other beds. 



I had no opportunity of examining any of the rocks further 

 eastward, which form the base of the trap formation, but since those 

 already described form part of a series of strata having a vertical 

 thickness of about 10,000 feet, it may be supposed that they afford 

 good average specimens of the whole. 



There is probably no one point, even in Europe, where within a 

 limited area, there are to be found such a number of mines, many 

 of them rich, well appointed and well managed j such a display of 

 beautiful mining machinery j or such magnificent stamp-works as 



