146 



IRON. 



This system of heating is represented in fi<v. 5 



Hiul 6. A A is the frame- 

 work itself, which is con- 

 structed of common bricks, 

 tin- interior being lined 

 with fire bricks, in order 

 to form the melting pot A', 

 and the exterior of it is 

 covered with sheet iron 

 plates, A", rivetted altoge- 

 ther, and bound with iron 

 circles a". The blast en- 

 ters the cupola alternately 

 by the different pipes a' 

 the lowest of them is used 

 to commence the process, 

 and as the height of the 

 melting metal rises in the 

 pot, they clmnge them in 

 order, so as always to blow 

 at a suitable height to the 

 bath of metal : the open- 

 ings of the pipes which are 

 not in use, are luted with 

 care, especially when they 



Fig. 5. 



Fig. 6 



have to support the pressure of the liquid contained 

 in the melting pot. The tap hole is at a, it is always 

 hermetically shut with a stopper, which may be lifted 

 out in a moment from the tap hole. 



The only modification that they have attempt- 

 ed to make, to improve the frame-work is in leading 

 to the top, a slope by which the charges of coal and of 

 pigs are thrown in ; the opening is usually shut by 

 the door b, which is lifted and attached by the little 

 chain b', during the very short time which is neces- 

 sary to throw in the charge. 



There are three cast iron plates, placed one above 

 another c, c,' c" of the same diameter as the frame- 

 work, and pierced in the centre with circular holes 

 a little greater than the diameter of the melting pot 

 A'. The first c" has a little jutting out c' " (fig. G), 

 serving as a point of support to the fanner by which 

 the furnace is supplied with the blast. The fanner 

 is put in motion by means of a belt led over a 

 drum on its axis, and connected with the steam en- 

 gine, or water wheel. The second plate c, has a 

 hole at the centre, a little greater than that of the 



first, that it may be protected against the action of 

 the heat. The third has a central hole, still a little 

 greater for the same reason, but its exterior diameter 

 is much less, so that it may leave upon the second 

 plate c' an open circular ring of from twelve to fif- 

 teen inches. Upon this third plate c, there are fixed 

 two concentric cylinders of plate iron D and D',which 

 are open below, but shut above, and the tops of 

 which are firmly joined by a sort of open joint 

 (/, d' ' . The exterior cylinder has two openings e and 

 e' ; one, that by which the cold air is introduced, 

 the other, that by which the air goes out after being 

 heated between the two coverings D and D' ; at the 

 distance of twelve or fifteen inches from the exterior 

 envelop D, a third envelop F, of brickwork, is 

 built, which is bound together with circles of iron, 

 as the frame-work itself. The bottom of this last, 

 rests upon the circular space, that the plate c left 

 open upon the plate iron c , and at its top it is shut, 

 by a convex iron plate //, upon which is erected a 

 vault of some non-conducting substance. The. iron 

 plate is pierced in the middle with a hole, which is 

 shut by means of a lid/', above which is put a stone 

 stopple G ; this order of things serves to inspect and 

 to clean the interior of the apparatus, as it is only 

 necessary to lift the stopple G and the lid/'. 



Above this opening at the top, which remains 

 always shut during the operation of melting, the 

 envelop F is carried down the side to its lower part; 

 there are two openings H H, into which are fixed the 

 strong iron pipes I I, which serve as a base and 

 support to the two chimneys K K ; the pipes I, I are 

 shut at their extremities by stopples i i, which re- 

 quire only to be lifted out when they wish to sweep 

 the chimney. 



The smoke rises and spreads itself in the interior 

 of the first envelop D', and after heating the sides, 

 goes out from this space by the little conduit d rf',then 

 passes under the vault//, in order to descend between 

 the exterior envelop F and the cylinder D, so that 

 it may arrive at the, two openings of the tubes 1 I, 

 and at the chimneys K K. 



The cold air enters by the opening e', between the 

 envelops D and D', and it comes immediately into 

 contact with the hot tops of these cylindrical enve- 

 lops : it comes also into contact with the sides of the 

 conduits d d' , which are also at a very high tempera- 

 ture ; thus heated against these surfaces, it descends 

 in the spaces comprised between the envelops D 

 and D', the one struck by the flame descending, the 

 other by the flame ascending, and it arrives at the 

 lower opening e, by which it escapes to the blast 

 pipes. A the blast pipe ought successively to be rais- 

 ed, so as to be put into the different openings a a a; as 

 the liquid metal accumulates in the melting pot, we 

 must have the means of making these changes with 

 facility. For that purpose there is placed in the open- 

 ing e, a fixed pipe L' L, which, after being bent, de- 

 scends vertically to L : in its straight portion, which 

 is bored very truly, there is fitted a smaller pipe 

 M M', capable of sliding in its interior like a piston 

 in the body of a pump. The lower extremity M, of 

 the pipe M M', has a curb m, upon which is fixed 

 the opening N of the bent N N' of which the other 

 extremity N' is adjusted in the opening; the two 

 curbs m and n are joined and held fast by the two 

 cramps P P. In order to shift the pipe, they loosen 

 the screws of the cramps P P, and lift them off, then 

 force up the pipe M M' into the pipe L' L, and re- 

 move the pipe N N' into an opening higher. The 

 pipes are then fixed to the cramps and curbs m and n 

 in this new position. 



We have thus endeavoured to describe the con- 

 struction of several forms of the hot blast furnace, 

 and shall conclude this part of our subject, by a 



