XII BULLETIN 42, UNITED STATES NATIONAL MUSEUM. 



PLATE II (Page 10). 



Hydraulic mining. — Working face of the North Bloomfield Hydraulic Mining Com- 

 pany, North Bloomfield, Califoruia. 



Shows along the foreground the sheet iron pipe in which the water is conveyed from 

 the ditch to the nozzles, at the end of this is a pile of stones placed upon it to keep it 

 steady, and beyond is a nozzle discharging a stream of water against the working face 

 of gravel. At the left, in the background, is another pipe and several nozzles. 



In the forei^round, near the center, are two bed-rock channels, one of which is in 

 use and throujjh which the water may be seen pouring. 



The full l)ackground shows the working face of gravel. 



The mau standing at the nozzle gives a gauge lor vertical distances. 



(Cat. No. 56595, U. S. N. M. From photograph. ) 



PLATE III (Page 26). 



SILVER . 



Silver milling, — Elevation of a mill for the chloridizing-roasting and amalgamation of 

 silver ores. 



At the top, on the left, is the stock house, for the reception of the ore from Ihe mines, 

 immediately below is the floor for the rock-breakers and for drying the ore. On the 

 next floor below and to the right are the stamps; on this floor a door leads to the Stete- 

 feldt furnace, the top of which may be seen farther along to the right. On the next 

 floor of the mill a door admits the poasted ore to the pans; just below and to the right 

 are the settlers. On the next floor are the agitators, and the door from this floor leads 

 to tlie retort house. (Cat. No. 51188, U. S. N. M. From Rothwell's "Cost of Milling 

 Silver Ores in Utah and Nevada.") 



PLATE IV (Page 28). 



SILVER. 



Silver milling. — Interior of a pan mill on the Comstock Lode, Storey County, Nevada. 



Along the right runs the track for bringing in the ore, prepared, either by simple stamp- 

 ing or stamping and roasting for milling. Next below is a row of pans, in which the 

 amalgamation is secured. Below again is a row of settlers, in which the amalgam and 

 mercury are separated from the ore. On the lowest level are the agitators, in which 

 a small amount of amalgam and mercury are removed. Just beyond the agitators is a 

 car loaded with the amalgam. 



(Cat. No. 51658, U. S. N. M. From photograph.) 



PLATE Y (Page 30). 



SILVER. 



Silver milling. — Exterior of the Ontario Mill, Park City, Summit County, Utah. 



The ore is drawn by teams from the mine to the mill along the road in the middle 

 ground at the right, which deliver it to the stock house, covered by the upper gable of 

 the main building. The second gable of the main bnilding covers the drying floor and 

 the stamp floor. To the right of the upper gable of the main building, partly concealed 

 by smoke, is the top of the Stetefeldt furnace; below and in front of this are the dust 

 chambers, and farther back, up the side of the hill, is the draft stack from the dust 

 chambers. 



