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BOOK IX.

are folded together. Since this kind of bellows does not give a vigorous blast,because they are drawn apart and compressed slowly, the smelter is notable during a whole day to smelt much more than half a centumpondium oftin.

Very good iron ore is smelted 55 in a furnace almost like the cupellationfurnace. The hearth is three and a half feet high, and five feet long andwide ; in the centre of it is a crucible a foot deep and one and a half feetwide, but it may be deeper or shallower, wider or narrower, according to whethermore or less ore is to be made into iron. A certain quantity of iron ore isgiven to the master, out of which he may smelt either much or little iron.He being about to expend his skill and labour on this matter, first throwscharcoal into the crucible, and sprinkles over it an iron shovel-ful of crushediron ore mixed with unslaked lime. Then he repeatedly throws on charcoaland sprinkles it with ore, and continues this until he has slowly built up aheap ; it melts when the charcoal has been kindled and the fire violentlystimulated by the blast of the bellows, which are skilfully fixed in a pipe.

55 In the following descriptions of iron-smelting, we have three processes described ;the first being the direct reduction of malleable iron from ore, the second the transition stagethen in progress from the direct to indirect method by way of cast-iron ; and the third amethod of making steel by cementation. The first method is that of primitive iron-workersof all times and all races, and requires little comment. A pasty mass was produced, whichwas subsequently hammered to make it exude the slag, the hammered mass being theancient “ bloom.” The second process is of considerable interest, for it marks one of theearliest descriptions of working iron in “ a furnace similar to a blast furnace, but much wider“ and higher.” This original German Stiickofen or high bloomery furnace was used for making“ masses ” of wrought-iron under essentially the same conditions as its progenitor the forge—only upon a larger scale. With high temperatures, however, such a furnace would, if desired,yield molten metal, and thus the step to cast-iron as a preliminary to wrought-iron becamevery easy and natural, in fact Agricola mentions above that if the iron is left to settle in thefurnace it becomes hard. The making of malleable iron by subsequent treatment of the cast-iron—the indirect method—originated in about Agricola’s time, and marks the beginning ofone of those subtle economic currents destined to have the widest bearing upon civilization.It is to us uncertain whether he really understood the double treatment or not. In the aboveparagraph he says from ore “ once or twice smelted they make iron,” etc., and in De NaturaFossilium (p. 339) some reference is made to pouring melted iron, all of which would appearto be cast-iron. He does not, however, describe the 16th Century method of converting castinto wrought iron by way of in effect roasting the pig iron to eliminate carbon by oxidation,with subsequent melting into a “ ball ” or “ mass.” It must be borne in mind that puddlingfor this purpose did not come into use until the end of the 18th Century. A great deal ofdiscussion has arisen as to where and at what time cast-iron was made systematically, butwithout satisfactory answer ; in any event, it seems to have been in about the end of the14th Century, as cast cannon began to appeal about that time. It is our impression thatthe whole of this discussion on iron in De Re Metallica is an abstract from Biringuccio,who wrote 15 years earlier, as it is in so nearly identical terms. Those interested will find atranslation of Biringuccio’s statement with regard to steel in Percy’s Metallurgy of Iron andSteel, London, 1864, p. 807.

Historical Note on Iron Smelting. The archseologists’ division of the historyof racial development into the Stone, Bronze, and Iron Ages, based upon objects found intumuli, burial places, etc., would on the face of it indicate the prior discovery of coppermetallurgy over iron, and it is generally so maintained by those scientists. The metallurgistshave not hesitated to protest that while this distinction of “ Ages ” may serve thearchseologists, and no doubt represents the sequence in which the metal objects are found,yet it by no means follows that this was the order of their discovery or use, but that ironby its rapidity of oxidation has simply not been preserved. The arguments which maybe advanced from our side are in the main these. Iron ore is of more frequent occur-rence than copper ores, and the necessary reduction of copper oxides (as most surfaceores must have been) to fluid metal requires a temperature very much higher than does thereduction of iron oxides to wrought-iron blooms, which do not necessitate fusion. The com-paratively greater simplicity of iron metallurgy under primitive conditions is well exempli-fied by the hill tribes of Northern Nigeria, where in village forges the negroes reduce iron