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BOOK VII.

and it is nearly as long as the furnace ; only at the front end does it touchthe mouth of the furnace, everywhere else on the sides and at the backthere is a space of three digits, to allow the charcoal to he in the open spacebetween it and the furnace. The muffle is as thick as a fairly thick earthenjar ; its upper part is entire ; the back has two little windows, and each sidehas two or three or even four, through which the heat passes into the scorifiersand 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 thelittle windows, or small holes, there are cut away three semi-circular notcheshalf a digit high, and on each side there are four. The back of the muffleis generally a little lower than the front.

A —Broad little windows of muffle. B—Narrow ones. C —Openings in the

BACK THEREOF.

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The crucibles differ in the materials from which they are made, becausethey 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 anuncia measure; in these the ore mixed with fluxes is melted, and they are usedby those who assay gold or silver ore. Some are triangular and muchthicker and more capacious, holding five, or six, or even more undue ; inthese copper is melted, so that it can be poured out, expanded, and testedwith fire, and in these copper ore is usually melted.

The cupels are made of ashes ; like the preceding scorifiers they aretray-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 mustbe said about the material from which they are made, and the methodof making them. Some make them out of all kinds of ordinary ashes ; theseare not good, because ashes of this kind contain a certain amount of fat,whereby such cupels are easily broken when they are hot. Others makethem likewise out of any kind of ashes which have been previouslyleached ; of this kind are the ashes into which warm water has been infusedfor the purpose of making lye. These ashes, after being dried in the sun ora furnace, are sifted in a hair sieve; and although warm water washes away the