FURNACES FOR SMELTING IRON.

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XIV. If the bottom of the focus be damp, or the stoneshave not been thoroughly dried, or the passage beneath is im-properly constructed, &c., the same disadvantages are to heapprehended; the fuel is unprofitably and uselessly spent, alarge quantity of calcareous stone must be added, whereby thequality of the iron is deteriorated; not to mention that less thanhalf the usual charge of ore must be introduced.

XV. If the blast be not duly proportioned to the dimen-sions of the furnace and fire-hearth, the smelting is injured.For, 1. The mass of liquefied iron is not moved as it should he.

| 2. The scoriae are not separated from the metal. 3. Nor is

there a sufficient supply of air to the combustible matter; thereis, therefore, a want of fire in the charcoal, and consequently,of effect on the ore, which must he compensated by an increasedquantity of fuel.

XVI. If the passage or orifice for the blast be too horizontal,1. The mass of iron is not set in motion by the air. 2. Theblast is immediately carried away to the upper parts, but is notdiffused towards every side, so as to exert an equal action onthe charcoal; the latter, therefore, is consumed, without the orebeing properly melted. 3. When, however, the focus or stelleis longer and narrower, this orifice ought to be horizontal; ifoblique, the mass of iron might cool; which must be guardedagainst by the combustion of an undue proportion of charcoal.

XVII. If the position of the orifice for the blast be toooblique, the melted ore cools round the opening of the bellows ;the cold air passing to the middle of the mass, which it coolsand frequently hollows out, as experience demonstrates. Thisis often seen under the opening, a cold hollow being formed inthe middle of the metal.

XVIII. If the due proportion of fuel and ore be not observed,thus if too much charcoal be introduced, then, 1. The iron maybe vitrified, and partially converted into scoriae: and the masswill appear glassy, silvery, and sparkling; also very brittle, andlighter than otherwise; in short, of the worst quality. 2. Toi say nothing of the useless consumption of charcoal. Thus theproper quantities must be ascertained by particular signs.

XIX. But if there be more ore than charcoal, 1. The iron willindeed be duly calcined, yet not smelted. 2. The stony part