Steel. 
geneous matter than ours, and are generally much richer, 
as they usually yield about 70 per quintal of pure iron, 
whereas the average of ours is not more than 30 or 40* ; 
add to this, that the Swedish ores are smelted in wood 
fires, which gives the iron an additional superiority. 
Iron instruments are case-hardened by heating them in 
a cinder or charcoal fire 5 but if the first be used, a quan- 
tity of old leather or bones must be burnt in the fire, to: 
supply the metal with carbon. The fire must be urged 
by a pair of bellows to a sufficient degree of heat, and the 
whole operation is usually completed in an hour. 
The process for case-hardening iron is in fact the same 
as for converting iron into steel, but not continued soi 
long, as the surface only of the article is to be impregna- 
ted with carbon. Some attempts have been made to give 
cast-iron, by case-hardening, the texture and ductility of 
steel ; but they have not been very successful. Table 1 
and pen-knife blades have been made of it ; and, whem 
ground, have had a pretty good appearance ; but then 
edges are not firm, and they soon loose their polish, ! 
Common table knives are frequently made of this metaL 
The cementation of iron converts it into steel, a substance 
intermediate between crude and malleable iron. 
The furnaces for making steel are conical buildings ; 
about the middle of which are two troughs of brick or 
fire-stone, which will hold about four tons of iron in the 
bar. At the bottom is a long grate for fire. The steel 
furnace, however, is not well adapted for description. I 
shall therefore avail myself of an accurate drawing, which 
was communicated to me by a gentleman conversant with 
the manufacture, and which is copied in the plate. A 
layer of charcoal-dust is put upon the bottom of the trough, 
* The iron made from the ore found in the neighbourhood of 
Sheffield, contains a great deal of phosphate of iron or siderite| 
Which renders the metal brittle when cold. I doubt tills, T. Q 
