[ 8 9 ] 



refining of metals or regulufes ; with the ftruo 

 ture and materials of the ovens, the fuel and 

 quantities of it employed, the time for each 

 operation, and the preparatory cautions, in- 

 cluding the picking, pounding, warning, fift- 

 ing, and uftulating of the ores ; and drawings 

 of the various machines and tools ufed for each 

 purpofe. 



4. The places from whence the various gems 

 or precious ftones are procured, with their 

 prices on the fpot the ground and ftrata where- 

 in they are found, and the figure or form of 

 each kind before being cut, whether determi- 

 nate and general, or accidental. 



5. The manner of manufacturing thofe iin- 

 menfe quantities of falt-petre annually exported 

 from the Eaft Indies; the foil employed for 

 the lixivium, and the manner of preparing the 

 foil. Are any animal or inflammable iubftances 

 added to it ? By what means is lixivium pre- 

 cipitated ? Is an alkali ufed for that purpofe, 

 and how is the alkali procured ? Is any ufe made 

 of the remainder of the lixivium after the pre- 

 cipitation of the faltpetre ? Is the lixivium 

 boiled, and infpiffated by fire for the cryftal- 

 lifation, or by the heat of the fun ? 



6. If borax be artificial, in what manner and 

 from what fubftances is it made ? If native, in 

 what ftrata and foil does it lie in ? 



7. How far has the knowledge, value, and 

 life of metals extended amongft nations ? 



The END. 



