138 Tmndulion of Key's Esia>/S. 



bulk, which not being the case in the point in question, it can- 

 not be admitted as the cause of the increased weight of which 

 I am speaking. I add in conclusion, that air, forcibly con- 

 densed in a balloon full of it, at its escape from it reduces its 

 weight, so far from increasing it, as Scaliger pretends. It is 

 true, this occurs in that instance only. 



ESSAY XIX. 



It is not soot that increases the weight of the caU. 

 1 read in the 10th chapter of the sixth book of the Chemical 

 Secrets of Libavius* , (for I have not seen it elsewhere,) that Cse- 

 salpinhas written, that it is a thing worthy of admiration that 



* " Cum metallutn Indicum, quod stannum Indicum et calcem vocant, 

 igoibus exploraremus, id quod prius erat gravissimum, in levissimam 

 favillam, et telas instar arauearura, fuliginemque pompholygi simileoi 

 redigi mirabamur. Transmutatio nimirum itidem pondus variat, noa 

 sola alteratio, qualis videtur esse in laterculis. Hi enim crudi, leviores 

 sunt quam cocti, et tamen perdiderunt humiditatem adlierentem ignibus. 

 Hue pertinet et Modestini Fachsii (a german chemist) quaestio, qui fiat in 

 examine metallico, res ignem passse, non sine detrimento favillarum pon- 

 derosiores inveniantur, quam nondum illatae. Si enim testam, plumbum, 

 metallum et cupellam ponderes ante examen, omnia sunt leviora quam 

 post, iterum ad libellam revocatis scoriis, testA, stanno seu massula et 

 cupeiia, cum tamen de plumbo mullum perierit. Andreas Caesalpinus, de 

 inetallicis, lib. iii, c, 7, scribit admiratione diguum esse, quod plumbum 

 nigrum ustum in fornace, donee cinis fiat, pondere crescat octoaut decern, 

 pro singulis centenariis, putatque idem fieri quod lateribus in fornace 

 coctis, qui et ipsi post assationem, graviores redduutur, cum oppositum 

 deberet fieri, absumptk multa eorum substantia in igni. Vult autem in 

 loco deperditae accedere fuliginem ignis, quae adhasrens lateribus in poris 

 coudensetur, quod magis fiat in plumbo, quia in furno reverberii flamma 

 super cineres reflectatur, ibique reponat suam fuliginem : argumento, 

 quod si iterum cinis in plumbum vertatur, moles diminuatur, reliquo 

 abeunte in excrementa ; unde concludit, ustione minui plumbum ; im- 

 bribus augescere. Ex dictis facile respondeas Fachsio evenire quaesitum 

 ob plunibi pondus auctum crematura ; sed Caesalpini ratio vel k Tyronibus 

 physicis ridebitur, qui colligent sic etiam calcem vivam debcre fieri gra- 

 viorem, nee posse id fieri a levissima ignis fuligiuc." — Libavii, yllchymiit 

 AixaiM, Lib, vi, c. 10. Fraucofurti, M.DC.LX 



