THE DAWN OF MODERN CHEMISTRY 17 



rence and changes of the metals — the sulphur of the philosophers — and 

 similarly with respect to arsenic and mercury. Upon these vague and 

 variously formulated hypotheses Paracelsus founded his more consistent 

 theory. 



All matter was, according to Paracelsus, constituted of three prin- 

 ciples, sulphur, mercury and salt. Sulphur, he explains, is that which 

 burns — the principle which renders bodies in any degree combustible 

 and yielding heat. Mercury was that principle of bodies which renders 

 them liquid or volatile, which enables them to melt on heating or to 

 pass off as a vapor by distillation or volatilization. Salt was the prin- 

 ciple which resists the action of heat — the ash or the non-combustible 

 and non-volatile constituents of matter. It will be observed that this 

 is a generalization of the properties of substances based upon the obser- 

 vation of their behavior towards the various degrees of heat to which 

 they were subjected in the customary processes of roasting, distillation, 

 ignition or reduction (this word also we first find in Paracelsus). 



The doctrine of the three principles of Paracelsus possessed that 

 advantage over the Aristotelian elements — fire, water, earth, air — in 

 that it was more closely related to experiment and experience and not 

 so purely metaphysical. It could serve as a kind of working hypothesis 

 to help understand the results of chemical experiment. The tria prima 

 received early recognition in chemistry. The very celebrated work 

 called the "Triumphal Chariot of Antimony." written about 1600 and 

 passed off on the public as a translation of an early manuscript by an 

 alleged Benedictine monk, Basil Valentine, adopted and helped to give 

 a wider circulation to this theory. It became almost universally ac- 

 cepted by the chemists of the seventeenth • century, and such popular 

 text-books as those of the French chemists, Christopher G-laser and 

 Nicholas Lemery, placed it at the foundation of chemical theory (the 

 latter as late as 1713). 



In the latter part of the seventeenth century, Becher introduced a 

 variation of this theory, by placing, instead of sulphur, a terra pingnis, 

 as the combustible constituent, fat or oil having, in so far as its com- 

 bustibility is concerned, a similar behavior to sulphur — for mercury 

 and salt he substituted a terra mercurialis (mercurial earth) and a terra 

 lapidis (or stony earth), 



This in itself was no advance, but Becher's pupil, Stahl, and his 

 followers elaborated this sulphur of Paracelsus or terra pinguis of 

 Becher into the idea of a more abstract heat substance, phlogiston, while 

 the less useful hypotheses of the mercury and salt gradually disappeared. 



In the eighteenth century under the influence of such able chemists 

 as Scheele, Black, Cavendish and Priestley the phlogiston theory became 

 the most inspiring theory to stimulate the observation and researches 

 of chemists. Only at the close of the eighteenth century when the 



VOL. LXXXVII. — 2. 



