Mr. G. F. Rodvvell on the Theory of Phlogiston. 19 



and it was believed that the added substance helped by its own 

 combustibility to expel the volatile parts of the metal. 



Geber observed that lead increases in weight during calcina- 

 tion*; and Cardanus added the observation that the gain amounts 

 to one-thirteenth the weight of the lead taken. Now Cardanus, 

 following some of the ancients, supposed everything to possess 

 a certain life, and that life was " a celestial heat" in fact the 

 "subtilis ignis" of other writers. When metals are calcined 

 they die, the celestial heat is dissipated, and they become heavier, 

 for the same reason that animals are heavier when dead than 

 when living ; for celestial heat tends upwards, and is the cause 

 of lightness f. Paracelsus had a somewhat similar idea as re- 

 gards the separation of the innate heat of the substance sub- 

 mitted to calcination. " By calcination," he writes, " is sepa- 

 rated watery moisture, fat, natural heat, odour, and whatever 

 else is combustible "J. Csesalpinus, in a very matter-of-fact 

 way, attributed the increase of weight to soot, which he imagined 

 became mixed with the metal during calcination ; others attri- 

 buted it to the retention of the " vapours of charcoal," or the " vo- 

 latile salt of charcoal," and some to matter removed from the 

 calcining vessel. In the midst of these diverse opinions there 

 appeared in 1625 the Praxis Chymiatrica of Jean Hartmann, 

 containing a chapter by Hamerus Poppius, "De Calcinatione An- 

 timonii per radios solares." When antimony was calcined by 

 converging the rays of the sun upon it by means of a lens, Pop- 

 pius found that a gain of weight was apparent, just as when it 

 was calcined in a furnace ; it was obvious, therefore, that the 

 gain could not arise from the assimilation of soot, or the "va- 

 pours of charcoal," or from any of the supposed causes men- 

 tioned above. A few years later (in 1629) the matter was in- 

 vestigated by Jean Rey a physician of Bergerac ; and the results 

 of his inquiry were published in an essay Sur la recherche de la 

 cause pour laquelle I'estain, et le plomb augmentent de poids quand 

 on les calcine. Rey attributed the increase of weight to the 

 absorption of thickened air ("Pair espessi ,} ) ; and the following, 



* Gebiri Philosophi ac Alchemistce Maximi de Alchemia, 1531, cap. 35. 

 " Sermo in Saturno." 



t Nam plumbum cum in cerusam vertitur, ac uritur, tertia decima parte 

 sui ponderis augetur. Hoc fit quia calor ccelestis evanescit : nam certum 

 est adjici nihil, et tamen crescit ; cum igitur parratio etiam in animalibus 

 videatur, quse graviora morte fiunt, quoniam exhalante anima secum calor 

 etiam, ac quicquid ab illo est elaboratum evanescit : manifestum est cor- 

 pora metallica et lapides ipsos etiam vivere." — Hieronymi Cardani 

 Medici Mediolanensis De Subtilitate lib. xxi. (Parisiis, 1551), lib. v. 

 " De Mixtione et Mixtis imperfectis, seu metallicis." 



X De Rerwn Natura, lib. viii. 



C 2 



