322 THE CANADIAN NATURALIST. [Vol. vll. 



compactness and shades of colours, interstratified with conglo- 

 merates and sandstones. 



According to Macfarlane, "the constituent of the traps of the 

 Portage Lake District are principally felspar of the labradorite 

 species, and chlorite of a species allied to delessite, with which 

 are found occasionally mica, small quantities of magnetite, and 

 perhaps of augite and hornblende."* He considers the charac- 

 teristic trap of the region to consist of: — 



Delessite 46-36 



Labradorite 47-43 



Pyroxene 5-26 



Magnetite 95 



100 00 



The mines in the immediate vicinity of the Lake are on the 



amygdaloidal trap. Many have been opened both on the north 



and south shores, but those only on the Pewabic lode — the 



Quincy, Pewabic, and Franklin mines — have returned profit to 



I their shareholders. Of these three, the best worked, and therc- 



l fore most successful, is and has been the Quincy, and we shall 



therefore describe it as being a typical, though the best example, 



of its class. 



': It was opened in 1849, and has been worked uninterruptedly 



^ ever since, stemming the tide of low prices when almost every 



other mine was carried down the current. 



The lowest level is at 1330 feet along the dip of the bed, and 

 therefore on the incline of the shaft from the surface, and the 

 longest level is 1600 feet. Tlie shafts and all the workings are 

 opened in productive ground, where that can be followed ; but as 

 the walls of the copper-bearing bed are never well defined, and 

 as tracts of rich ground abruptly alternate with stretches of barren 

 rock, there is found considerable difiiculty in keeping to the lode, 

 as it is called. Moreover, from being pinched and poor, or even 

 barren, it will suddenly bulge to 20 or 30 feet of rich rock. The 

 hanging ivall is composed of a fine-grained, compact, bluivsh trap, 

 but the characteristic trap beneath is coarse-grained and amyg- 

 daloidal, and approaches in appearance to the copper-bearing 

 rock. 



The copper bed, however, while likewise generally permeated 



♦Geology of Canada, 1866, p. 152. 



