BOOK XII. 



575 



A— Caldron. B— Tank. C— Cross-bars. D— Ropes. E— Little stones. 



By the third method vitriol is made out of melanteria and sory. If 

 the mines give an abundant supply of melanteria and sory, it is better to 

 reject the chalcitis, and especially the misy, for from these the vitriol is impure, 

 particularly from the misy. These materials having been ,dug and thrown 

 into the tanks, they are first dissolved with water ; then, in order to recover 

 the pyrites from which copper is not rarely smelted and which forms a sedi- 

 ment at the bottom of the tanks, the solution is transferred to other vats, 

 which are nine feet wide and three feet deep. Twigs and wood which float 

 on the surface are lifted out with a broom made of twigs, and afterward all the 

 sediment settles at the bottom of this vat. The solution is poured into a 

 rectangular leaden caldron eight feet long, three feet wide, and the same in 

 depth. In this caldron it is boiled until it becomes thick and viscous, when 

 it is poured into a launder, through which it runs into another leaden caldron 

 of the same size as the one described before. When cold, the solution is 

 drawn off through twelve little launders, out of which it flows into as many 

 wooden tubs four and a half feet deep and three feet wide. Upon these tubs 

 are placed perforated crossbars distant from each other from four to six 

 digits, and from the holes hang thin laths, which reach to the bottom, with 



