. De re metallica. Metallurgy; Mineral industries. 228 BOOK VII. and it is nearly as long as the furnace ; only at the front end does it touch the mouth of the furnace, everywhere else on the sides and at the back there is a space of three digits, to allow the charcoal to lie in the open space between it and the furnace. The muffle is as thick as a fairly thick earthen jar ; its upper part is entire ; the back has two little windows, and each side has two or three or even four, through which the heat passes into the scorifiers and melts the ore. In place of little windows, some muffles have sm
. De re metallica. Metallurgy; Mineral industries. 228 BOOK VII. and it is nearly as long as the furnace ; only at the front end does it touch the mouth of the furnace, everywhere else on the sides and at the back there is a space of three digits, to allow the charcoal to lie in the open space between it and the furnace. The muffle is as thick as a fairly thick earthen jar ; its upper part is entire ; the back has two little windows, and each side has two or three or even four, through which the heat passes into the scorifiers and melts the ore. In place of little windows, some muffles have small holes, ten in the back and more on each side. Moreover, in the back below the little windows, or small holes, there are cut away three semi-circular notches half a digit high, and on each side there are four. The back of the muffle is generally a little lower than the A-B ROAD LITTLE WINDOWS OF MUFFLE. B—NARROW ONES. C—OPENINGS IN THE BACK THEREOF. The crucibles differ in the materials from which they are made, because they are made of either clay or ashes ; and those of clay, which we also call " earthen," differ in shape and size. Some are made in the shape of a mod- erately thick salver (scorifiers), three digits wide, and of a capacity of an uncia measure ; in these the ore mixed with fluxes is melted, and they are used by those who assay gold or silver ore. Some are triangular and much thicker and more capacious, holding five, or six, or even more unciae ; in these copper is melted, so that it can be poured out, expanded, and tested with fire, and in these copper ore is usually melted. The cupels are made of ashes ; Uke the preceding scorifiers they are tray-shaped, and their lower part is very thick but their capacity is less. In these lead is separated from silver, and by them assays are concluded. Inasmuch as the assayers themselves make the cupels, something must be said about the material from which they are made, and the method of making the
Size: 2937px × 851px
Photo credit: © Paul Fearn / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookauthoragricolageorg14941555, bookcentury1900, booksubjectmin
