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BOOK IX.

sized tin-stone which melts quickly, but less of the large ones which meltslowly, and a moderate quantity of the medium-sized which holds the middlecourse. Those who do not smelt the tin-stone in furnaces made sometimeswide, sometimes medium, or sometimes narrow, in order that great lossshould not be occasioned, throw in first the smallest size, then the medium,then the large size, and finally those which are not quite pure ; and the blastof the bellows is altered as required. In order that the tin-stone throwninto the furnace should not roll off from the large charcoal into the forehearthbefore the tin is melted out of it, the smelter uses small charcoal; first someof this moistened with water is placed in the furnace, and then he frequentlyrepeats this succession of charcoal and tin-stone.

The tin-stone, collected from material which during the summer waswashed in a ditch through which a stream was diverted, and during the winterwas screened on a perforated iron plate, is smelted in a furnace a palm widerthan that in which the fine tin-stone dug out of the earth is smelted. Forthe smelting of these, a more vigorous blast of the bellows and a fiercer fireis needed than for the smelting of the large tin-stone. Whichever kind oftin-stone is being smelted, if the tin first flows from the furnace, much of it ismade, and if slags first flow from the furnace, then only a little. It happensthat the tin-stone is mixed with the slags when it is either less pure orferruginous—that is, not enough roasted—and is imperfect when put intothe furnace, or when it has been put in in a larger quantity than was neces-sary ; then, although it may be pure and melt easily, the ore either runsout of the furnace at the same time, mixed with the slags, or else it settlesso firmly at the bottom of the furnace that the operation of smelting beingnecessarily interrupted, the furnace freezes up.

The tap-hole of the forehearth is opened and the tin is diverted into thedipping-pot, and as often as the slags flow down the sloping floor of the build-ing they are skimmed off with a rabble ; as soon as the tin has run out ofthe forehearth, the tap-hole is again closed up with lute mixed with powderedcharcoal. Glowing coals are put in the dipping-pot so that the tin, after ithas run out, should not get chilled. If the metal is so impure that nothingcan be made from it, the material which has run out is made into cakes to bere-smelted in the hearth, of which I shall have something to say later; if themetal is pure, it is poured immediately upon thick copper plates, at first instraight lines and then transversely over these to make a lattice. Each ofthese lattice bars is impressed with an iron die ; if the tin was melted outof ore excavated from mines, then one stamp only, namely, that of theMagistrate, is usually imprinted, but if it is made from tin-stone collected onthe ground after washing, then it is impressed with two seals, one theMagistrate’s and the other a fork which the washers use. Generally, threeof this kind of lattice bars are beaten and amalgamated into one mass with awooden mallet.

The slags that are skimmed off are afterward thrown with an iron shovelinto a small trough hollowed from a tree, and are cleansed from charcoal