*3^ Of the Sulphur 



here more clofely to the fulphur than the iron-par- 

 ticles do. But all that can be hence inferred is, 

 that the copper-particles may be more adapted for 

 volatilifation than the iron -particles are •, as it mud 

 be allowed, that the groffeft earthy metal-particles, 

 as iron and copper, nay all imperfect metals, may 

 barely, by the action of the fire, without any addi- 

 tional affiftance, be volatilifed. 



What may help to remove all difficulties, is the 

 having in our eye the two following important and 

 repeatedly confirmed rules : 



(i.) That fome matters, when accompanied, or 

 combined with fomething, even not fo effential to 

 the defign, ufually fhew themfelves, both paffively 

 and aMively, of a very different habitude; either 

 more adapted and active, or more powerful and 

 operative, than when employed feparately. 



(2.) That metallic earths are in their mineral 

 ftate of a quite different aptitude, than when 

 brought into a metallic body, and fmelted. Silver, 

 as a metallic body, will be readily allowed to remain 

 unvolatilifed, but combined with common fait, 

 will prove fugitive. The vitriolic acid is one of 

 the moft powerful, penetrative, active things in 

 nature, yet deprived of the inflammable earth it 

 poffeffes in the fulphur --mixtion^ it can never pro- 

 duce the fame effects that it does, when treated in 

 the form of fulphur : and the effects of fulphur it- 

 felf upon metallic earths are owing to its combined 

 ftate in the mineral of fulphur, namely, the py- 

 rites. 



The grounds of thefe two practical rules depend 

 fometimes barely on giving a fteadinefs and body 



to 



