184 Miscellanies. 



the whole length of the furnace, which is from thirteen to fourteen 

 feet ; it is fourteen inches wide and is from ten to twelve inches be- 

 low the bottom of the troughs. The height of the culminating point 

 of the vault above the trough is five feet six inches. The bottom of 

 the troughs is nearly on a level with the floor, so as to prevent the ne- 

 cessity of lifting the bars of iron very high in charging the furnace. 



The flame rises between the two troughs, passes underneath, and 

 circulates around them by openings, or vertical and horizontal canals, 

 o, fig. 1, 2, and 3; it issues from the furnace by an opening H, in 

 the centre of the vault, and by holes t, which communicate with 

 chimneys placed in the angles. Some furnaces are noted for a greater 

 number of chimneys symmetrically disposed around the structure. 

 In others, the partitions are pierced with vent holes, which are opened 

 during the cooling. The whole furnace is situated in a vast cone of 

 brickwork from twenty five to thirty feet in height, open at the top. 

 This cone increases die draught, regulates it, and conducts the smoke 

 out of the establishment. 



The furnace has three doors, two T, fig. 2, above the troughs 

 which serve for the introduction and withdrawal of the bars ; they are 

 seven or eight inches square. In each of them is fixed an iron plate, 

 turned up at the edges, on which the bars rub without injuring the 

 wall. A workman enters by the middle opening P, to arrange the 

 bars; and by the holes S, fig. 1, in the sides of the trough, the trial 

 bars are drawn out. 



The bars are arranged in beds, in the cementing troughs, with 

 powdered charcoal. They are about three inches wide and four 

 lines thick. They must not be placed too near each other, lest they 

 become soldered together. The last layer (which fills the trough?) 

 is formed of clay, and is four or five inches thick. 



The furnace is gradually heated, attaining its greatest intensity ua 

 about eight or nine days. The cooling which must be progressive, 

 lasts five or six days, and the whole operation from eighteen to 

 twenty days, and sometimes longer, according to the intended quality 

 of the steel. There are consumed, during this time, about thirteen 

 tons of pit coal. 



Fabrication of cast steel. — Cast steel is made of blistered steel or 

 steel of cementation. It is broken into piece , put into an eartbern 

 crucible, and heated in a common wind furnace. This furnace is a 

 foot or fourteen inches square, and two feet de< p. 



