BOOK IX. 



427 



with moss, are placed upside down in the openings of the lower pots, where they 

 are joined with lute, lest the quicksilver which takes refuge in them should 

 be exhaled. There are some who, after the pots have been buried, do not fear 

 to leave them uncemented, and who boast that they are able to produce no 

 less weight of quicksilver than those who do cement them, but nevertheless 

 cementing with lute is the greatest protection against exhalation. In this 

 manner seven hundred pairs of pots are set together in the ground or on a 

 hearth. They must be surrounded on all sides with a mixture consisting of 

 crushed earth and charcoal, in such a way that the upper pots protrude to a 

 height of a palm above it. On both sides of the hearth rocks are first laid, 

 and upon them poles, across which the workmen place other poles transversely ; 

 these poles do not touch the pots, nevertheless the fire heats the quick- 

 silver, which fleeing from the heat is forced to run down through the moss 

 into the lower pots. If the ore is being reduced in the upper pots, it flees 

 from them, wherever there is an exit, into the lower pots, but if the ore on 

 the contrary is put in the lower pots the quicksilver rises into the upper pot 

 or into the operculum, which, together with the gourd-shaped vessels, are 

 cemented to the upper pots. 



A HEARTH. B POLES. C HEARTH WITHOUT FIRE IN WHICH THE POTS ARE PLACED. 

 D ROCKS. E Rows OF POTS. F UPPER POTS. G LOWER POTS. 



