. Library of universal knowledge. A reprint of the last (1880) Edinburgh and London edition of Chamber's encyclopaedia, with copious additions by American editors. coal or coke, it contains no sulphuret of iron or other injurious ingredients. The Rus-sian and Swedish furnaces smelt with charcoal, and on this, as mucli as on their pureores, depends tiie high reputation of their iron. A solitary charcoal-furnace at Ulvcr-stone in England, and another at Lorn in Scotland, are still working—the only relics oftimes past, when this was the only fuel employed. As a preliminary process to the actual s
. Library of universal knowledge. A reprint of the last (1880) Edinburgh and London edition of Chamber's encyclopaedia, with copious additions by American editors. coal or coke, it contains no sulphuret of iron or other injurious ingredients. The Rus-sian and Swedish furnaces smelt with charcoal, and on this, as mucli as on their pureores, depends tiie high reputation of their iron. A solitary charcoal-furnace at Ulvcr-stone in England, and another at Lorn in Scotland, are still working—the only relics oftimes past, when this was the only fuel employed. As a preliminary process to the actual smelting in the blast-furnace, clay and black-band ironstones are generally roasted. This is accomplished by breaking the ore intosmall pieces, spreading it in open heaps on the ground, and mingling it more or less with,small coal according to the nature of the ore. Blackband commonly contains enough ofcarbonaceous matter to burn without the addition of coal. The pile, which may containfrom one to several thousand tons of ore, is lighted at the windward end, and burnsgradually along, aided by occasional fires in the sides, till the whole heap has undergone. Fig. 1. Hot Blast-furnace. calcination, the time required for this purpose being generally about a month. Some-times the operation of roasting is performed in close kilns, instead of open heaps, a modeby which the ore is considered to be more uniformly roasted, and with considerably lessfuel. Of late years, the kilns are often heated by the waste gases of the calcination, clay ironstone loses from 25 to 30, and blackband from 40 to 50 per centof its weight, the loss consisting chiefly of carbonic acid and water, but sulphur andother volatile substances are also dissipated in the process. The roasting also convertsthe protoxide and carbonate of iron into peroxide, which prevents the formation of slagsof silicate of iron, such slags, owing to the difficulty of reducing them, causing a loss ofiron. In this cou
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