Indian Science and Technology in the Eighteenth Century: Some Contemporary European Accounts c23.s5.t4: Refineries
Indian Science and Technology in the Eighteenth Century: Some Contemporary European Accounts c23.s5.t4
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Refineries
c23.s5.t4.1
The refinery is as crude in its appearance, and as novel in its construction as the furnace, to which it seems to have been purposely adapted: two refineries being required for one smelting furnace; to construct it they use the small cubit of 20 digits, or what is still more available, the space or distance between the tips of the thumb and little finger of a middle sized man when extended without force, two such spans being considered equal to the cubit; the first process is to arrange a number of square unburnt bricks, as in the ground plan (Diagram V, fig 1) in which a, a, a, a, are the walls—A is the chimney, B the refining furnace, C the seat of the refiner, and D the anvil; see also fig 2 for a side view of it—divided in the middle for the purpose of showing the interior structure, in which E is a piece of crude iron under the process of decarbonisation; the dimensions of the chimney are not material—but it is usually about one cubit broad, one deep and six in length; the oval part where the operator sits is altogether a fanciful appendage, being merely a mound of earth in which a log of wood is inserted for receiving the anvil—and its elevation serves the further purpose of giving the workmen a purchase in using the hammer; when the walls of the chimney are finished, the top is covered with unburnt bricks of an oval shape, flat below and convex above and these are luted together by a plastering of clay—fig. 3 is a front view—showing the opening of the furnace and Diagram VI exhibits the refinery complete, with the refiner at work on his seat, the bellows-man plying the bellows, and various implements lying about—A the outside of the chimney—B a mound of earth to strengthen its wall—C the refining furnace—D a piece of crude iron undergoing the process of decarbonisation (in dotted lines)—E the bellows-man plying the bellows—F the refiner with an iron spike in his hand regulating the operation (the dotted lines showing the interior of the furnace)—G a thick plate of iron placed at the bottom of the refinery (in dotted lines)—H a fosse for the hammerman—I the anvil—K implements, and L a heap of charcoal.
c23.s5.t4.2
The furnace of the refinery is the only part which requires skill in its construction, and this is usually done by the operator himself; its geometrical outline is represented (Diagram V, fig 4) and its construction is as follows. Rule a line AB equal five parts, divide it into six—set off four of these divisions for the top—let fall a perpendicular from the centre C—set off three divisions from C to D for the depth—rule a line through D—parallel to AB and make it two divisions, now rule the outline—bisect the perpendicular and the centre parallel will be equal to three divisions.
c23.s5.t4.3
The centre parallel is the most important part of the furnace and next to it is the accurate adjustment of the angle of the blast; I have frequently seen the Indian refiners obliged to discontinue their work on account of some error in this point; the usual measure for the former is the span above mentioned applied both longitudinally and transversely as in Diagram V, fig 1, B where a ground plan of the furnace is exhibited—the inner circle of which corresponds with the centre parallel of fig 4—this measure never differs much from 8 inches, and that quantity may be assumed as a fair average;—the outer circle *b* of the same figure is indefinite—the space between the two—being merely a slope, chamfering from the inner edge, and gradually expanding, until it is lost in the sides of the furnace, so that in fact it is reverberatory; with regard to the blast, it is absolutely necessary that it should be directed, at an angle of about 12 degrees, upon the opposite edge of the inner circle or to the point c fig 1, B; the natives have no instruments to enable them to do this exactly but the working of the furnace soon tells them where there is an error and they know well enough how to correct it;—the bellows resemble those of the smelting furnace, but instead of the wooden nozzle, they are furnished with long iron tubes—as in Diagram V, fig 5 which are so placed, that the angle of the blast thrown through them is 24 degrees, the same as that of the wooden nozzle.
c23.s5.t4.5
DIAGRAM VI