In Cumberland, Northumberland, Durham and latterly the United States, the reverberatory furnace is used only for roasting the ore, and the oxidized ore is then reduced by fusion in a low, square blastfurnace (a "Scottish hearth furnace") lined with cast iron, as is also the inclined sole-plate which is made to project beyond the furnace, the outside portion (the "work-stone") being provided with grooves guiding any molten metal that may be placed on the "stone" into a cast iron pot; the "tuyere" for the introduction of the wind was, in the earlier types, about half way down the furnace.
The smelting zone always has a bosh and a contracted tuyere section.
GG; Flanges on the ore bucket; P, Cinder notch; HH, Fixed flanges on the top of RR', Water cooled boxes; the furnace; S, Blast pipe; J, Counterweighted false bell; T, Cable for allowing conical K, Main bell; bottom of bucket to 0, Tuyere; drop.
R, Keys holding lid of tuyere E, Goose-neck.
16, so that the blast, which has been let on just before this, entering through the great number of tuyere holes in the bottom, forces its way up through the relatively shallow layer of iron, throwing it up within the converter as a boiling foam, and oxidizing the foreign elements so rapidly that in some cases their removal is complete after 5 minutes.