1 873.] Colorado Gold Mines. 19 



have been removed; the slopes, if filled with poor ground, 

 are blocked for hundreds of feet, so that it is generally im- 

 possible, without great cost, to examine the ground left 

 standing, or, if the stopes be empty, they are vast caverns, 

 with the roof so feebly supported by a few slender props 

 that it is with greatest risk one enters them. These defects 

 of the past — due, in chief measure, to the faults of the su- 

 perintendents, though in part to the ignorance of the miner, 

 who went to his task, from a farm in the East or cattle- 

 grazing on the plains without any previous knowledge, far 

 less education — will, it is to be hoped, not disfigure future 

 operations. When better methods of treating the ore are 

 introduced, the miner will wish to reach the once unremu- 

 nerative but now valuable ground left standing, and the 

 difficulty and expense of doing so will teach him that it 

 would have been cheaper to have properly opened and kept 

 open his mine from the first. 



Methods of Treatment. 



Battery Amalgamation. — At the outset of mining, 12 and 

 14 years ago, when the rich surface quartz carried free gold 

 abundantly, stamp-batteries, supplied with riffles and such 

 appliances for catching the free gold, were employed. When 

 the sulphurets were reached these failed altogether to secure 

 the precious metal, and amalgamated copper plates sup- 

 planted the riffles. But it was some time before the mill-men 

 understood the necessity of thoroughly cleansing and amal- 

 gamating the plates. To arrest the sulphurets blankets are, 

 in some mills, placed below the amalgamated plates, and 

 the blanketings ground in pans, the mercury in the concen- 

 trate sufficing for the amalgamation of the small quantity 

 of gold thus saved. The tailings are frequently further 

 concentrated in tins — those called " hand-buddies." Round 

 buddies have been tried, but found too slow, and to require 

 more attention than the rough impatient workman will 

 bestow. 



The stamps are run slowly, never exceeding 30 strokes, — 

 a higher speed interfering with the battery amalgamation, 

 by discharging on the plates too great a volume of water and 

 slime. Amalgamated copper plates are fixed within the bat- 

 tery, under the charging and discharging openings, and form 

 an apron in front of the discharge to feet to 12 feet long, 

 and set at an angle of io° to 14 . Mercury is added every 

 two hours, through the charging-slit, in quantities to suit 

 the richness of the ore : three times as much is introduced 

 as is afterwards recovered. 



