664 GEOLOGY AND MINING INDUSTRY OF LBADVILLE. 



branch pipe, T, which in this case acts as a main. At Smelter I, working with two 

 furnaces, each furnace induction pipe is similarly placed in direct communication with 

 each blower; but the general system adopted in the camp, at smelters working with 

 two or more furnaces, is to connect all the blowers with a main pipe, R, from which 

 the branch pipes T distribute the blast to the induction-pipes of each furnace. The 

 whole system of blast-pipes, including the tuyeres, but with the exception of the canvas 

 wind-bags, is made of galvanized sheet iron. 



Blast-pipe system The most complete and perfect system of blast-pipes, from 

 which this description will be made, is applied at Smelter C. At Smelter F the 

 arrangement is similar in every respect; at the other smelters the arrangement is very 

 nearly the same, and if there are slight modifications of the general system there are 

 no improvements on it. Two blowers, A and B (Fig. 1, Plate XXXI), communicate with 

 the main pipe, R', by means of the pipes E, each of which is provided with dampers 

 or gliding-valves, F, regulating the draft, and with safety-valves, 8, regulating the 

 pressure. The safety-valves are set to a pressure of about nine-eighths of an inch of 

 mercury. The draught is regulated in the main pipe, R', by means of dampers, F, or 

 sliding valves worked by a lever, h h' (see Fig. 5, Plate XXIX). A similar damper, 

 F" (Fig. 1, Plate XXXI), allows the excess of blast to escape from the main pipe. The 

 branch pipes T', provided with dampers F, worked like the preceding, allow the 

 introduction of the proper amount of blast required by each furnace ; each pipe, T, 

 communicates at Z" with a manometer. The general arrangement of the induction- 

 pipe I and a branch pipe, J, is clearly shown in the same figure, and a glance at Fig. 

 5, Plate XXIX, indicates the connection of the branch pipes J with the tuyeres N 

 by means of the canvas hose K. Thus by the preceding disposition an even pressure 

 of blast is secured in a main pipe, from which the proper amount required for each 

 furnace is taken at will. As far as the distribution of blast is concerned, the blast- 

 pipe system just described is absolutely perfect; but it lacks an important element, 

 which would render invaluable services in smelting, namely, the means of ascertaining 

 the volume of blast blown into each furnace during a certain lapse of time. This could 

 easily be determined by the use of a meter similar to those used for the measurement 

 of illuminating gas in cubic feet. This meter should be placed lietween the damper F 

 of the branch pipes T and the induction-pipes of each furnace. In tins way atmos- 

 pheric air might be considered as one of the elements of the smelting charges, and by 

 this means weighed or measured with as much accuracy as the fuel itself, with whit h 

 it bears the closest relation. This important point will be insisted upon in the dis- 

 cussion of the smelting reactions. 



SMELTING OPEEATIONS IN GENERAL. 



Drying of the furnace When the furnace is new or when an old furnace has been 

 recently relined, it is first of all carefully dried by means of a slow charcoal or wood 

 fire kept steadily burning and slowly increasing in temperature for several days, every 

 precaution being taken to prevent the escaping moisture from loosening the masonry. 



When heat is perceptible on the outside of the walls of the furnace the drying is 

 completed. The fire is allowed to burn out and the furnace left to cool. This done, 

 the crucible is immediately lined either with steep in every part or with tamping in 



