684 GEOLOGY AND MINING INDUSTRY OF LEADVILLE. 



Two boilers, 40 incbes by 16 feet, worked at a pressure of 60 pounds to tbe square 

 iucb, supply a 70-horse power engine (cylinder 14 by 24 incbes), and a second engine 

 of 50 borse-power, witb its boilers, is kept ready for use in case of need. Tbis engine 

 was tbe one formerly used at tbese works before tbey bad attained tbeir present smelt- 

 ing capacity. 



Tbe 70 borse-power engine drives tbree Baker blowers, one Root blower, two 

 large Blake crusbers, a set of Cornisb rolls, and a slag-boisting macbine. Tbe furnace- 

 room is 120 by 40 feet, and contains four furnaces, smelting about one bundred and 

 twenty tons of ore in twenty-four bours. Tbe ventilation of tbis room will be sbowa 

 in tbe description of tbe dust-cbambers. Tbe slagbeap is connected witb tbe feeding- 

 floor by au inclined plane boistiug-macbiue, similar to tbe one used at smelter B, and 

 used also to carry tbe slag up to be resmelted. 



Furnaces — Smelter G bas tbree furnaces of equal sbape and dimensions, similar 

 to tbe one sbown in front elevation (Fig. 1, Plate XXXV), and one larger furnace, sbown 

 iu Fig. 2, Plate XXXV. Altbougb bnilt on tbe same general ]irinciples as tbe otber 

 furnaces of tbe camp, tbey offer a few interesting peculiarities in construction. Tbe 

 small furnaces are square (3 by 4 feet at tbe tuyeres), and tbeir cast-iron i)ilbirs 

 rest on tbe fire-brick lining of tbe crucible. Tbe water-jackets B are made of riveted 

 boiler-plates and are only four in number. Eacb side jacket is provided witb two 

 tuyere boles and tbe back jacket with one; but tbe furnace is worked witb tbe four 

 side tuyeres only. 



The main cast-iron plate sn])port bas a broad vertical flange, 0, which confines 

 tbe base of tbe outer walls C of tbe furnace shaft, the shaft itself being, as usual, lined 

 witb fire-bricks ; tbe outer wall is made of red bi-ick, braced at Q. 



These furnaces are fed through a single feed-bole placed at tbe back of each, 

 and provided witb :>beet-iron sliding doors. The whole portion of the furnace com- 

 prised between the feeding-floor and the damper of the stack is surrounded by a sheet- 

 iron jacket, J'. 



Tbe crucible of the furnace is framed iu strong cast-iron plates, and the frame of 

 tbe siphon-tap, lined witb steep, is made of strong- sheet iron. The smelting caj^acity 

 of each of tbese furnaces is 26 to 28 tons of ore ]>er twenty four bours, and the length 

 of runs is about 118 days. 



The large furnace represented in Fig. 2 is the only one of its kind used in Lead- 

 ville. Tbe lead siphon tap L is placed in front of tbe furnace, and on eacb side of tbe 

 furnace there are a fore hearth, X', and a slag-spoiit, Z7, alternately used for the tapping 

 of slag. In B' are seen tbe slag-pots, mounted on wheels. 



The water-jacket system is formed of four large water-jackets made of riveted 

 boiler-plates. The front and back jackets are eacb provided witb four tuyere-holes, 

 but tbe furnace is worked with only six tuyeres. Tbe dimensions at the tuyeres are 3 

 by 5 feet. Tbe main cast iron i)late support has a broad, vertical flange, 0, incasing 

 the base of the masoniy. 



The furnace is fed from two feed-holes, ZI, opened or closed by sheet iron sliding 

 doors. The feed-holes are placed in the side walls of this furnace, which correspond 

 to tbe front and back walls of other furnaces. Tbe pressure of blast used at smelter 

 G varies from five-eighths of an inch to ten eighths of an inch of mercury. Tbe capac- 

 ity of the large Raschette furnace, which has just been described, is 38 to 40 tons of oie 



