No. 2.J SPENCER — COPPER-MINING. 71 



III. — Notes on Copper Mining in the Lake Superior 

 Region. 



Under this head it is proposed to notice briefly the art of 

 mining as it has been applied to the Native Copper Mines of 

 Keweenaw Peninsula, and to give a short sketch of the finan- 

 cial condition of the industry. 



Ordinary blasting powder is almost entirely used. Nitrogly- 

 cerine and dualin have been introduced, but several accidents 

 having occurred, their use has been abandoned. One of the 

 most fatal of these accidents was at the Phoenix Mine, resulting 

 in the death of two mining captains and four other men. This 

 explosion took place in the office of the captains, while some men 

 were mixing the dualin with ordinary blasting powder, as the 

 mixture was usually fired with fusees and not by electricity. 

 There was a quantity of dualin cartridges in the building when 

 the accident happened, and although the concussion was so great 

 as to throw them several hundred feet, to the top of a high cliff, 

 many were afterwards picked up unexploded. In some places, 

 dualin was found unsuitable for blasting, as the action was such 

 as to bring down too much waste rock in certain directions, but 

 elsewhere it has rendered good service. 



As noticed before, the copper is obtained from beds and veins. 

 The beds which are worked dip at various angles from 26° (at 

 the Copper Falls Mine) to 56° (at the Quincy), while the dip 

 of the veins is usually greater than 73°. In almost all cases the 

 shafts fallow the inclinations of the beds or veins, changing with 

 their variations of dip; and in only a few instances are the 

 shafts perpendicular or straight throughout their whole depth. 

 Some shafts have been sunk without any engineering skill 

 whatever, and after thousands of dollars have been wasted, have 

 been abandoned, and others sunk at great expense, this being more 

 economic il than to straighten those that were so crooked. The 

 best work of engineering skill about Lake Superior is at the 

 Phoenix Mine, where an additional shaft was required. The 

 workings are on the side of a hill capped with a great thick- 

 ness of greenstone, and it was found that it would be less expen- 

 sive to sink a shaft at a low inclination, beneath the great bed 

 of diorite, than to sink one perpendicularly through it. The mine 

 Vol. VIII. e No. 2. 



