468 



BOOK X. 



the litharge flows out. Copper plates are placed on this part of the sole-stone 

 so that the silver-lead or other alloy may be more rapidly heated. 



A dome which has the shape of half a sphere covers the crucible. It con- 

 sists of iron bands and of bars and of a lid. There are three bands, each about 

 a palm wide and a digit thick ; the lowest is at a distance of one foot from the 

 middle one, and the middle one a distance of two feet from the upper one. 

 Under them are eighteen iron bars fixed by iron rivets ; these bars are of 

 the same width and thickness as the bands, and they are of such a length, that 

 curving, they reach from the lower band to the upper, that is two feet and 

 three palms long, while the dome is only one foot and three palms high. All 

 the bars and bands of the dome have iron plates fastened on the underside 

 with iron wire. In addition, the dome has four apertures ; the rear one, 

 which is situated opposite the channel through which the litharge flows out, 

 is two feet wide at the bottom ; toward the top, since it slopes gently, it is 

 narrower, being a foot, three palms, and a digit wide ; there is no bar at 

 this place, for the aperture extends from the upper band to the middle one, 

 but not to the lower one. The second aperture is situated above the 



A RECTANGULAR STONES. B SOLE-STONE. C AIR-HOLES. D INTERNAL WALLS. 

 E DOME. F CRUCIBLE. G BANDS. H BARS. I APERTURES IN THE DOME. 



K LlD OF THE DOME. L RlNGS. M PlPES. N VALVES. CHAINS. 



