SMELTING OPERATIONS. 665 



some parts only, viz, tbe dam, siphon, and siphon-tap. Steep or brasque is a mixture of 

 one part fire-clay and one part coke-dust, but more generally two parts fire-clay and' 

 one part coke-dust. Tamping is a simple lining of fire-clay. It is only used 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 np 

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

 The tuyere-holes of the water jackets are 'left open, as well as the tymp-stone and 

 the damper of the stack, in order to create a draft. The charcoal gradually becomes 

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

 blowiug-in begins. The tuyere holes of the water-jackets, witlrthe 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 the capacity of the furnace), are 

 sealed with pings of fire-clay and the wind-bags of the corresponding tuyeres are 

 tied np with strings. The tymp-stone is set in and the blast is then turned on at full 

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

 the lead-pot becomes red hot. 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, according 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 14 per cent, 

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

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

 the blowiug-in. When molten lead makes its appearance at the top of the siphon-tap 

 a few pieces 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 tymp-stone to ascertain their degree of 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 proceeding 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 hand, and of the fluxes and ore, 

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

 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 in the lower part of the shaft of the furnace immediately above the water- 

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

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



