684 GEOLOGY AND MINING INDUSTRY OF LEADVILLE. 



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

 incb, supply .1 70-horse power engine (cylinder 14 by 24 inches), and a second engine 

 of 50 horse-power, with its boilers, is kept ready for use in case of need. This engine 

 was the one formerly used at these works before they had attained their present smelt- 

 ing capacity. 



The 70 horse-power engine drives three Baker blowers, one Root blower, two 

 large Blake crushers, a set of Cornish rolls, and a slag-hoisting machine. The furnace- 

 rooin is 120 by 40 feet, and contains four furnaces, smelting about one hundred and 

 twenty tons of ore in twenty-four hours. The ventilation of this room will be shown 

 in the description of the dust-chambers. The slag-heap is connected with the feeding- 

 floor by an inclined plane hoisting-machine, similar to the one used at smelter B, and 

 used also to carry the slag up to be resmelted. 



Furnaces Smelter G has three furnaces of equal shape and dimensions, similar 

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

 in Fig. 2, Plate XXXV. Although built on the same general principles as the other 

 furnaces of the camp, they offer a few interesting peculiarities in construction. The 

 small furnaces are square (3 by 4 feet at the tuyeres), and their cast-iron pillars 

 rest on the fire-brick lining of the crucible. The water-jackets B are made of riveted 

 boiler-plates and are only four in number. Each side jacket is provided with two 

 tuyere holes and the back jacket with one ; but the furnace is worked with the four 

 side tuyeres only. 



The main cast-iron plate support has a broad vertical flange, 0, which confines 

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

 with fire-bricks ; the outer wall is made of red brick, braced at Q. 



These furnaces are fed through a single feed-hole placed at the back of each, 

 and provided with iiheet-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'. 



The crucible of the furnace is framed in strong cast-iron plates, and the frame of 

 the siphon-tap, lined with steep, is made of strong sheet iron. The smelting capacity 

 of each of these furnaces is 26 to 28 tons of ore per twenty four hours, 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. The lead siphon tap L is placed in front of the furnace, and on each side of the 

 furnace there are a fore hearth, i'', and a slag-spout, U, alternately used for the tapping 

 of slag. In B' are seen the 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 each provided with four tuyere-holes, 

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

 by 5 feet. The main cast iron plate support has a broad, vertical flange, 0, incasing 

 the base of the masoniy. 



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

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

 to the front and back walls of other furnaces. The pressure of blast used at smelter 

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

 ity of the large Raschette furnace, which has just been described, is 38 to 40 tons of 01 e 



