BOOK VII. 



225 



palm long and a palm wide ; small pieces of charcoal, after being laid thereon, 

 can be placed quickly in the furnace through its mouth with a pair of tongs, 

 or again, if necessary, can be taken out of the furnace and laid there. 



The iron assay furnace is made of four iron bars a foot and a half high, 

 which at the bottom are bent outward and broadened a short distance to enable 

 them to stand more firmly ; the front part of the furnace is made from two 

 of these bars, and the back part from two of them ; to these bars on both 

 sides are joined and welded three iron cross-bars, the first at a height of a palm 

 from the bottom, the second at a height of a foot, and the third at the top. 

 The upright bars are perforated at that point where the side cross-bars are 

 joined to them, in order that three similar iron bars on the remaining sides 

 can be engaged in them ; thus there are twelve cross-bars, which make 

 three stages at unequal intervals. At the lower stage, the upright bars are 

 distant from each other one foot and five digits ; and at the middle stage the 

 front is distant from the back three palms and one digit, and the sides are 

 distant from each other three palms and as many digits ; at the highest stage 

 from the front to the back there is a distance of two palms, and between the 

 sides three palms, so that in this way the furnace becomes narrower at the 

 top. Furthermore, an iron rod, bent to the shape of the mouth, is set into 

 the lowest bar of the front ; this mouth, just like that of the brick furnace, 

 is a palm high and five digits wide. Then the front cross-bar of the lower 

 stage is perforated on each side of the mouth, and likewise the back one ; 

 through these perforations there pass two iron rods, thus making altogether 

 four bars in the lower stage, and these support an iron plate smeared with 

 lute ; part of this plate also projects outside the furnace. The outside of 

 the furnace from the lower stage to the upper, is covered with iron plates, 

 which are bound to the bars by iron wires, and smeared with lute to enable 

 them to bear the heat of the fire as long as possible. 



As for the clay furnace, it must be made of fat, thick clay, medium so 

 far as relates to its softness or hardness. This furnace has exactly the same 

 height as the iron one, and its base is made of two earthenware tiles, one 

 foot and three palms long and one foot and one palm wide. Each side of the 

 fore part of both tiles is gradually cut away for the length of a palm, so 

 that they are half a foot and a digit wide, which part projects from the 

 furnace ; the tiles are about a digit and a half thick. The walls are similarly 

 of clay, and are set on the lower tiles at a distance of a digit from the edge, 

 and support the upper tiles ; the walls are three digits high and have four 

 openings, each of which is about three digits high ; those of the back part and 

 of each side are five digits wide, and of the front, a palm and a half wide, to 

 enable the freshly made cupels to be conveniently placed on the hearth, when 

 it has been thoroughly wanned, that they may be dried there. Both tiles 

 are bound on the outer edge with iron wire, pressed into them, so that they 

 will be less easily broken ; and the tiles, not unlike the iron bed-plate, have 

 three openings three digits long and a digit wide, in order that when the upper 

 one on account of the heat of the fire or for some other reason has become 

 damaged, the lower one may be exchanged and take its place. Through these 



