BOOK VII. 



241 



But it is better at first to add as much lead as is required to the ore which 

 needs melting, rather than afterward when the melting has been half finished, 

 that the whole quantity may not vanish in fumes, but part of it remain 

 fast. When the heat of the fire has nearly consumed the lead, then is the 

 time when the gold and silver gleam in their varied colours, and when all the 

 lead has been consumed the gold or silver settles in the cupel. Then as 

 soon as possible remove the cupel out of the furnace, and take the button out 

 of it while it is still warm, in order that it does not adhere to the ashes. This 

 generally happens if the button is already cold when it is taken out. If the 

 ashes do adhere to it, do not scrape it with a knife, lest some of it be lost and 

 the assay be erroneous, but squeeze it with the iron tongs, so that the ashes 

 drop off through the pressure. Finally, it is of advantage to make two or 

 three assays of the same ore at the same time, in order that if by chance 

 one is not successful, the second, or in any event the third, may be certain. 

 While the assayer is assaying the ore, in order to prevent the great heat 

 of the fire from injuring his eyes, it will be useful for him always to have 

 ready a thin wooden tablet, two palms wide, with a handle by which it may 

 be held, and with a sht down the middle in order that he may look through 

 it as through a crack, since it is necessary for him to look frequently within 

 and carefully to consider everything. 



A — Handle of tablet. B — Its crack. 



Now the lead which has absorbed the silver from a metaUic ore is con- 

 sumed in the cupel by the heat in the space of three quarters of an hour. When 

 the assays are completed the muffle is taken out of the furnace, and the 

 ashes removed with an iron shovel, not only from the brick and iron furnaces, 

 but also from the earthen one, so that the furnace need not be removed from 

 its foundation. 



From ore placed in the triangular crucible a button is melted out, from 

 which metal is afterward made. First of aU, glowing charcoal is put into 

 the iron hoop, then is put in the triangular crucible, which contains the ore 

 together with those things which can liquefy it and purge it of its dross ; 

 then the fire is blown with the double bellows, and the ore is heated until 

 the button settles in the bottom of the crucible. We have explained that 

 there are two methods of assaying ore, — one, -by which the lead is mixed 



