SMELTING OPERATIONS. 665 



some parts only, viz, the daui, siphon, and siphon-tap. Steep or brasqne is a mixture of 

 one part fireclay and one part coke-dust, but more generally two parts tire-clay and 

 one part coke-dust. Tamping is a simjjle lining of fireclay. It is only nsed for certain 

 parts of crucibles entirely lined with fire-bricks. 



Blowing-in or starting of the furnace — The furnace, being ready for work, is filled ui> 

 from the hearth to the throat with charcoal, which is set on tire at the hearth zone. 

 The tuyere-holes of the water jackets are left open, as well as the tympstone and 

 the damjier of the stack, in order to create a draft. The cbarcoal gradually becomes 

 incandescent to the very throat, and when this zone has attained a low red heat the 

 blowing-in begins. The tuyere holes of the water jackets, with the exception of from 

 two to four of the holes nearest to the front, and in which the respective tuyeres are 

 inserted (the number of tuyeres set in depending on tlte capacity of the furnace), are 

 sealed with pings of fireclay and the wind-bags of the corresi)onding tuyeres are 

 tied lip with strings. The tympstone is set in and the blast is then turned on at full 

 pressure. A long flame issues from the siplion-tap, and this is kept on steadily until 

 the lead-pot becomes red lior. The clay stoppers of the tuyere-holes in the water- 

 jackets are then removed and all the tuyeres let in. The blast at this point is regu- 

 lated to the normal pressure, and the furnace is ready for the filling of the crucible. 



Filling- of the crucible — Bars of bullion always kept in reserve for this purpose, and 

 in amount from four to twelve tons, accoriling to the capacity of the crucible, are thrown 

 in at the feed-holes with more fuel. This is done gradually in the proportion of three 

 bars of bullion, or 300 pounds, to eight shovels of charcoal, or about li per cent, 

 of fuel. According to the capacity of the furnaces, from one hundred to two hundred 

 and fifty busbels of charcoal are consumed in the preliminary operation constituting 

 the blowingin. When molten lead makes its appearance at the toj) of the siphon-tap 

 a few ])ieces of live charcoal are placed upon it to prevent it from cooling, and the fur- 

 nace is ready for charging. 



Charging of the furnace — Old slags are first of all thrown in the furnace, as a kind of 

 test of the temperature of the furnace, which is not ready so long as the slags are not 

 perfectly fluid. The head smelter or his assistant opens from time to time the tap hole 

 in the tympstone to ascertain their degreeof fluidity, and the regular charging begins 

 only when they run quite freely. This point being attained the charges are disposed 

 inside of the furnace next to the walls, a depression being left in the center for the 

 charging of the fuel. This mode of charging is the one generally adopted, but there 

 are variations in the mode of mixing the materials forming the smelting charges. At 

 some smelters fuel is first thrown in, then old slags, over the -lags the fluxes, and above 

 the fluxes the ore. At others fuel is mixed with old slags and fluxes are mixed with 

 the ore. Lastly, and this is the mode of iiroceeding mostly adopted, the slags, fluxes, 

 and ore are mixed together and the fuel is kept separate. At the most successful 

 smelters the mixing of fuel and old slags, on the one band, and of the fluxes and ore, 

 on the other, is prevalent. Whatever mode of mixing the materials of the smelling 

 charges is used, the manner in which they are distributed in the furnace is the same; 

 that is, fuel is always thrown in the center of the furnace and the charge distributed 

 on the sides next to the walls. This seems scarcely a good plan, as it favors the growth 

 of accretions iu the lower part of the shaft of the furnace immediately above the water- 

 jackets, in the very place where their removal offers the greatest difliculties. It would 

 seem that, if in each alternate charge the process was reversed and the fuel alternately 



