TC 



-wood mixed with the charge, are kept as loosely as possible in the furnace. The 

 time of roasting, during which the furnace is in the main left to itself, lasts 

 from 20 till 30 days. After the roast lias cooled down, what has heen badly 

 roasted is put aside for a second calcination, while the well roasted masses, 

 whether silver — , copper — , iron — , or lead — ores, are smelted all in the same 

 universal furnace ("' Fukidoko "). 



SMELTING. 



The furnace consists in a hollow made in the ground, covered with brasque, 

 of nearly hemispherical form, with a diameter of l l / 2 ' — Vs', which receives the 

 requisite blast from ordinary smith's-bellows (" Fuigo ") through 1 or 2 nozzles 

 of clay. These bellows are hand-box-bellows, the valves packed with badger's 

 skin ; the piston-rod is moved backward and forward by a coolie, who draws it 

 out with the hand and pushes it back with the foot. Usually two such bellows 

 are used at each furnace. The bellows furnish about 4 cub.' air per piston stroke 

 = about 120 cub.' air per minute, of atmospheric pressure. 



The tuyeres open into the furnace in the upper border of the same, and in 

 order to prevent the direct ascent of the blast, but on the contrary spread 

 the latter over the entire space of the furnace, a vaulted roof of clay extends 

 above the orifices of the tuyeres as far as half-way into the furnace. The fur- 

 nace is separated from the bellows by a back -wall ; the products of combustion 

 escape through a chimney, built of frame-work and covered with loam, which is 

 supported partly by the back- wall, partly by pillars, and commences about 7' 

 above the bottom of the kiln. 



To blow in the furnace, the latter is filled with dark charcoals ; fire is lit 

 only before the tuyeres, and the bellows are put gently in motion. Gradually 

 the fire is increased, charcoals and charge are thrown in a hpap over the fur- 

 nace, and thus the charge is reduced to a state of fusion. When the furnace is fill- 

 ed with molten masses nearly to the tuyeres, then the blast is stopped, the heap 

 consisting of red-hot charge and burning charcoals is pushed aside, the fire is 

 slackened with water, the liquid slags are withdrawn from the molten bath, 

 and the smelting is continued in (he above manner, until at last the whole fur- 

 nace is filled with liquid metal respectively matt, whereupon the contents are 

 either laddled out, or lifted off in discs, or, although rarely, tajjped. The red- 

 hot furnace is then repaired with some clay, and a similar smelting repeated. 

 When also this, and may be yet a third one, has been done, then the furnace 

 has become so much impaired, that it is unfit for further work ; it is then cooled 

 with water, repaired with brasque, and warmed over the night, in order to be 

 ready for use the following day. 



