GENERAL ARRANGEMENT OF FURNACES. 661 



vanized sheet-iron, provided whh sliding valves, I, used to observe the interior of the 

 furnace, and also as safety-valves, for rhey are left partially opened. The front jackets 

 are always provided with an open space, V, varying in shape and dimensions, and 

 closed with a plug of tapping clay. This plug is called the tymp-stone. The tap-hole 

 Z is perforated through the tymp stone for the exit of molten slag. 



Circular furnaces (Plate XXVII). The circular furnaces are constructed on the 

 same principles as the square ones, differing only in that their masonry is always 

 hidden from view by a wrought-iron casing or jacket, J', painted black. This jacket is 

 made of riveted wrought iron plates about one-fourth inch thick. The round furnoces, 

 like the square ones, are made of two independent parts ; the masonry supported on a 

 cast-irou plate, 0, resting on cast-iron pillars, P ; and the crucible or hearth A, upon 

 which rest the circular water-jackets J?, always made of wrought-iron plates riveted. 

 The interval between the water-jackets and the masonry is also filled in with fire-brick, b. 

 The main c;ist-iron plate support is provided with a circular vertical flange, 0', and with 

 four projecting horizontal flanges, 0", corresponding to the pillars. These horizontal 

 flanges are supported by brackets r ; they rest on the flanges (designated also by 0") 

 of the capitals of the pillars, supported by brackets t. The masonry jacket </' (Fig. 3) 

 is incased by the flange 0' of the main cast-iron plate support 0, and rests on this 

 plate, as does the masonry C'. The wall C" is made of fire-bricks. The stack E, a con- 

 tinuation of the jacket J', is not lined with fire-bricks. A wooden hood, W, and chimney, 

 W, are placed in front of the furnace, above the slag-gutters. The hexagonal induction 

 blast-pipe / supplies the branch pipes J and the tuyeres N with the blast. K repre- 

 sents the canvas hose or wind-bags connecting the branch pipes J wi h the tuyeres N. 



The hearth or crucible A and fore-hearth X are made of strong cast-iron plates, 

 firmly bound together and covered with a cast-iron plate, d. The lead-pot, which pro- 

 jects from the crucible, is framed in a wrought-iron or cast-iron box. The fore-hearth is 

 provided with two slag-gutters, U. The hearth A', fore-hearth X', and lead-pot L are 

 made of steep. The lead pot and crucible communicate, as in the case of square fur- 

 naces, by means of the siphon L'. The circular water-jackets are made of two sections, 

 firmly bound together. Each section is provided with a water-supply pipe,./!/, at base, 

 and an outlet, Jf, at top, to carry off hot water. In these jackets no other feeders are 

 used. 



Holes in the jackets allow the introduction of the tuyeres. The horizontal section 

 (Fig. 2) through the tuyeres shows the disposition of the blast apparatus in the furnace. 

 The deflecting elbow or sheet-iron flue F' forms the connection between the chimney 

 D and the dust-condensing chamber D'. The stack E is provided with a damper, G. 

 The furnace has but one feed-hole, H, with its sliding door 8. 



Blast apparatus. The blast apparatus in general use in Leadville consists of rotary 

 positive blasts, driven by steam power; of galvanized-iron pipes, for the distribution 

 of the blast; and of thin galvanized-iron tuyeres, connected with the branches of the 

 blast-pipes by means of canvas hose or wind-bags. The blower mostly adopted is 

 Baker's rotary forced-blast blower, but at one smelter Root's forced-blast blower is 

 also in use. The average pressure of the blast introduced in the furnaces is one inch 

 of mercury. The following table gives the character, capacity, etc., of the blowers 

 used at each smelter: 



