26 Mr. G. F. Rodwell on the Theory of Phlogiston. 



with substances rich in phlogiston, the latter is reabsorbed, and 

 the metal is the result. Sulphur is composed of sulphuric acid 

 plus phlogiston ; therefore sulphur minus phlogiston is sulphuric 

 acid. Phlogiston is spoken of as possessing " predisposing affi- 

 nity " for substances. We perceive, by reference to the ideas 

 of Becher regarding the constitution of bodies, that he consi- 

 dered sulphur a compound of the combustible principle with 

 the "universal acid," the principle of acidity. Stahl adopted 

 the idea of the " universal acid ; " and some of the later phlogis- 

 tians regarded sulphuric acid in that light. 



Shortly before Lavoisier, by an admirable series of experi- 

 ments, proved the fallacy of the theory, the principal properties 

 of hydrogen were made known, and in this gas the phlogistians 

 took refuge as a last resource. Hydrogen, they said, is phlo- 

 giston; when certain metals are dissolved in acid it visibly 

 escapes ; and when the calces of these metals are heated in hy- 

 drogen, they become metals again by absorbing the gas. The 

 analogy with hydrogen appeared complete in some respects ; but 

 the properties conferred upon the supposed phlogiston of Stahl 

 were utterly different from those of hydrogen in many respects. 

 The perversion of the original theory did not, however, end with 

 the attempt to prove the identity of hydrogen with phlogiston ; 

 for after the abandonment of the theory in France it still found 

 supporters in Germany ; and some of the more ardent (among 

 them Gren) preferred to grossly garble the theory rather than 

 relinquish it. When, however, in 1792 the Academy of Sciences 

 of Berlin abandoned the theory and adopted the views of Lavoi- 

 sier, the controversy which for some years had raged between 

 the phlogistians and the antiphlogistians was virtually at an end, 

 although a few of the former carried their views into this 

 century. 



# VI. Of the syncretistic nature of the theory of Phlogiston. 



Having traced the development of the phlogistic theory, let us 

 now consider its nature and influence. 



Phlogiston was a new name for an old principle. We have seen 

 that the idea of the existence of a subtle fire innate in matter has 

 pervaded physical philosophy from the earliest times. Phlogiston 

 was another name for the "pure fire" of Zoroaster, the " are/cve- 

 kov irvp " of Zeno, the " subtilis ignis " of Lucretius, the " ele- 

 mental fire" " astral fire" "sulphur " or " sulphureous principle" 

 of the Chemists, the "color ccelestis" of Cardanus, the "sideric 

 sulphur" of Paracelsus, the "materia ccelestis" of Descartes, 

 the " terra inflammabilis " of Becher. The functions of this 

 entity had been varied by different thinkers almost as much 

 as its name, until Descartes gave them accurate definition. The 



