Translation of Key's Essays. 141 



place alluded to above,) that in the examination of metals the 

 vessel, the cupel, the lead and the metal examined, are alto- 

 gether heavier after the process than before they had undergone 

 the fire, notwithstanding the loss of much matter that flies off 

 in fumes, which could not happen but from a great deal of the 

 above-mentioned air adhering to the whole, a thing which till 

 now has not been clearly understood. Thus the calcining 

 vessel itself may become heavier, which I beg the Sieur Brunn 

 to take notice of. 



ESSAY XXI. 

 The vapours of the charcoal do not increase the weight. 

 I have been told, (if truly I know not,) that one of my inti- 

 mate friends *, a man of profound knowledge, and the most 

 polished and solid judgment, to whom the Sieur Brun made the 

 same request as to me, suffered himself to believe that the in- 

 creased weight in question proceeds from the vapours of the 

 charcoal, which, passing through the vessel, mix amongst the 

 calx, which I maintain is impossible. For if such vapours can- 

 not pass through a glass phial, a tin plate, an earthen pot, 

 (otherwise our boiled waters, our sauces, our pottage, would be 

 infected with it,) how can they pass through a vessel of iron, 

 whose material is so much stronger ? If the most subtle air 

 cannot penetrate it, (what otherwise would my ./Eolipile be 

 worth ?) how shall these grosser vapours ? But if they could 

 penetrate it, what shackles would they find in the calx to retain 

 them ? Why should they finish their course there ? The heat, 

 by its violence, expels from the tin and the lead the moisture 

 which connected their parts, driving far away all the metallic 

 vapours, although natural to them ; and it will leave these 

 foreign vapours ! There is no probability in it. Oh ! truth, 

 how dear art thou to me, who canst make me contend against 

 so dear a friend t ! 



[To be continued.] 



* Deschamps, according to M. Gobet, who says he was a doctor of 

 physic at Bergerac, a skilful mathematician, and a pupil of the celebrated 

 Rodulphus Suellius, professor at Leydeu, in 1009. 



i Honest John Rey might fairly say with the philosopher of old, "Ami- 

 cus Plato, amicus Socrates, sec' magis arnica Veritas ;" an adiniral)le- 

 motto for all who cultivate Science as she should be cultivated, not its' 

 support a system or a sect, but to developc truth. 



