The accustomed shape in which the raw material is used as a medium of exchange is in spear heads[22] or in spades. Throughout the whole district of the Upper Nile these answer all the purpose of our current coin. Although the superficial veins of iron ore, for hundreds of miles, do not differ much in their appearance, there are only certain localities which produce an ore that, under the primitive mode of smelting, yields a remunerative supply of genuine metal. One of these prolific veins is found in the proximity of Kurshook Ali’s Seriba. With a perseverance for which I could not have given them credit, the natives have dug out trenches some ten feet deep, from which they have obtained a material very like our roe-stone. Considerable quantities of red ochre are discovered, but they are not turned to any account, through ignorance of a proper way of manipulation.
Just before the commencement of seed-time, in March, the Dyoor make a general move away from their huts, partly for the purpose of dragging the rivers for fish, and partly to busy themselves with iron-smelting in the woods. In the shaded centre of a very wooded spot they construct their furnaces of common clay, making them in groups, sometimes as many as a dozen, according to the number of the party. Their wives and children accompany them, and carry all their movables. In the midst of the wilderness, otherwise so desolate, they form a singular picture. The stems of the trees gleam again with their lances and harpoons; on the branches hang the stout bows ready for the buffalo hunt; everywhere are seen the draw-nets, hand-nets, snares and creels, and other fishing-tackle. There is a mingled collection of household effects, consisting of gourd-shells, baskets, dried fish and crocodile, game, horns, and hides. On the ground lie piles of coals, of ore, of cinders, and of dross. Petherick, the first explorer of this Dyoor district, has given a very accurate account of their primitive method of smelting iron, so that I may be repeating in a degree what has been related before: many things, however, there are which appeared to me under a somewhat different aspect.
Dyoor Smelting-furnace.
DYOOR SMELTING FURNACE.
The smelting-furnace is a cone, not more than four feet high, widening at the top into a great goblet shape. So little deviation was there in the form of any that I saw that all seemed to me to be erected on precisely the same model. One obstacle to the construction of larger furnaces is the extreme difficulty of preventing the mass of clay from cracking in the process of drying. The cup-shaped aperture at the top communicates by a very small throat with the cavity below, which is entirely filled with carbons. Into the upper receiver are thrown fragments of ore, of about a solid inch, till it is full. The hollow tunnel extends lower than the level of the ground; and the melted mass of iron, finding its way through the red-hot fuel, collects below in a pile of slag. At the base there are four openings: one of these is much larger than the others, and is used for the removal of the scoriæ; the other three are to admit the long tewel-irons, which reach to the middle of the bottom, and keep the apertures free for the admission of air. Without stoking, the openings would very soon become blocked up with slag. In reply to my inquiry I was told that bellows are never employed; it was said that too fierce a fire was injurious, and caused a loss of metal. A period of a day and a half, or about forty hours, is requisite to secure the product of one kindling. When the flames have penetrated right through the mass of ore until they rise above it, the burning is presumed to be satisfactory.
Amongst the Bongo the furnaces are different, being generally constructed in three compartments, and fitted with bellows. They also place layers of ore and fuel alternately.
The deposit of metal and fuel is heated a second time, and the heavy portion, which is detached in little leaflets and granules, is once more subjected to fire in crucibles of clay. The particles, red-hot, are beaten together by a great stone into one compact mass, and, by repeated hammering, are made to throw off their final dross. Nearly half of the true metal is scattered about during the progress of the smelting, and would be entirely lost if it were not secured by the natives. In regard to its homogeneousness and its malleability, the iron procured in this way is quite equal to the best forged iron of our country.
The Dyoor and the Bongo appear almost equally ignorant about charcoal-burning. They understand very little about the exclusion of air from the furnaces, or of burning their wood in piles: their science seems limited to the combustion of small fragments heaped up over one another till the fire below them is choked, or subdued by pouring water upon the top. I am not aware whether the other negroes have mastered the secret of charcoal-making; but if what has been said about the Dyoor holds good about Africa in general, it accounts at once for the remarkable fact that in spite of the abundance of the crude material, iron is so little employed. There is a universal absence of lime, so that stone erections are quite unknown.