tn the Pyrites. 189 



a certain ore, without any the lead addition of ca- 

 Jamy, if not a real corporal zink 9 yet its proximate 

 infallible fign, the genuine pbilof&pbical zvooL But 

 without any fuch experience, and from a flight 

 knowledge of metallic bodies, the derivation from 

 lead to tin is eafy ; but then in the fire this pro- 

 duction is extremely difiipable, zink burning away 

 as quickly as it is produced, fo that it is not procu- 

 rable in our huts in its living ftate -, not from a de- 

 fect of the proper matter for the purpofe, as we 

 may have fuch in furnace-fragments ; but then it is 

 no longer to be catched living (from the following 

 circumftances, namely, the degree of the fire/ the 

 nature of the furnaces and additions, and the inex- 

 perience of the operator) but dead, and in its afhes, 

 from which, indeed, it is again recoverable *. 



Formal zink, foQil calamy, and furnace- fragments, 

 or cadmia fcrnacum, appearing fo different bodies, 

 who could imagine thele three fhould be pofTefTed 



of 



* Pott y in his diuertation on xink, makes zink to arife 

 from the metalliiation of an alkaline earth, whence he deduce-. 

 its friability in acid-, and that it confifts of a mercurial, vitre- 

 fcible, and a tender inflammable earth; the mercurial earth 

 appearing fron: ing in the fire, its commixtion with 



mercury, and its mercurirkation ; the inflammable earth, from 

 its ready afcenfion, when treated per ft in the fire, -as alfo from 

 tre; :cs vitrefcible earth, from its vitre- 

 fcericy, which Henckel firft accomplished in the vehement heat 



• ind-furnace. fc>u r . its fpeciflc nature, and mixtion, he 

 -*- to confift principally in the indeterminable, and fcarce 



perfectly imitable combination of a copious inflammable prin- 

 ciple, a!or.^ with a certain peculiarly alcalinc cnith : and to 

 this earth ia owing both ir 3 difficulty of vitrefcency (fuch a : > is 

 alfo obfervable in tin) fuperable only by a mod vehement de- 

 gree of fire, an-i the ufual bitternefs of calcarious earths in fo- 

 Jutions ; and if, by means of the inflammable earth, it changes 

 to a reguiine body, :: the caufe alfo why copper changes to a 



* colour. 



