152 NOTES ON THE NORTHWEST. 



superior stratum is called the " cap rock." The fissures 

 containing the ore frequently expand into large caverns. 

 They are generally, in this case, found studded with stalac- 

 tites of calcareous spar on the roof. 



In the clay diggings the ore occurs in detached fragments, 

 and is called "float mineral." 



The surface of the ground, in certain parts of the mining 

 district, is completely honejxombed with the shafts of the 

 diggers, to the danger of cattle and travellers. The work- 

 men descend into the shafts, and raise their mineral by 

 means of large tubs fixed to a rope and w^indlass. The 

 mineral is very pure, generally yielding about 80 per cent, 

 of lead. An analysis of two average specimens of galena 

 is given in Mr. Owen's report as follows : — 



1st spec. 2d spec. 



Sulphur ------ 16.00 14.63 



Lead - - 84.00 85.37 



100.00 100.00 



Mr. Owen, in his report to the government, gives the fol- 

 lowing statement of the process of mining : — 



" When a miner sets out in search of lead ore, he usually 

 begins by what is called ' prospecting ;' that is, on those 

 spots where surface or other indications lead him to expect a 

 discovery of ore, he commences digging holes or sinking 

 shafts, usually on the summit or the declivity of a hill. 

 Should he fail in the first attempt to reach gravel mineral, or 

 to come upon any signs of neighborhood to a fissure, he soon 

 abandons the spot, and begins to dig elsewhere. The ground 

 in many portions of the lead districts is found riddled with 

 such pits, called, in the language of the Wisconsin miner, 

 ' prospect holes.' Should he reach encouraging symptoms, 



