17 



Lavoisier proved by means of tlir balance that every case of rusting 

 of metals or oxidation, or of combustion, is accompanied by an increase 

 in -\vi-iirht at the expense of the atmosphere. He formed, therefore, the 

 natural opinion that the heavier substance is more complex than the 

 li^hter one. 25 The following remarkable experiment wa> madt> by 

 Lavoisier in 1774, and gave indubitable support to his opinion, which 

 was iii many respects contradictory to Stahl's doctrine. Lavoisier 



hypothesis, they should den-case in weight, because phlogiston is separated l>y oxidation. 

 Stahl speaks on this point as follows: 'I know well that metals, in their transformation 

 into earths, increase in weight. But not only does this fact not disprove my theory, but, 

 on the contrary, confirms it, for phlogiston is lighter than air, and, in combining with 

 substances, strives to lift them, and so decreases their weight ; consequently, a substance 

 which has lost phlogiston must be heavier.' This argument, it will be seen, is founded 

 on an improper understanding of the properties of gases, regarding them as having no 

 weight and as not being attracted by the earth, or else on a confused idea of phlogiston 

 itself, as it was first defined as imponderable. The conception of imponderable phlogiston 

 tallies well with the habit and methods of the last century, when recourse was often had 

 to imponderable fluids for explaining a large number of phenomena. Heat, light, 

 magnetism, and electricity were explained as being peculiar imponderable fluids. In this 

 sense the doctrine of Stahl corresponds entirely with the spirit of his age. If heat be 

 now regarded as movement or energy, then phlogiston also should be considered in this 

 light. In fact, in combustion, of coals, for instance, heat and energy are evolved, and 

 not combined in the coal, although the oxygen and coal do combine. Consequently, the 

 doctrine of Stahl contains the essence of a true representation of the evolution of energy, 

 but naturally this evolution is only a consequence of the combination going on between 

 the coal and oxygen. As regards the history of chemistry prior to Lavoisier, besides 

 Stahl's work (to which reference has been made above), Priestley's Experiments and 

 (>l>nrrr{t(iitfi an ])i/cri'/it Kin<7s of Air, London, 1790, and also Scheele's Opuscula 

 Chiinicfi et Phi/sic<i, Lips., 17NS-s ( .. '2 vols., must be recommended as the two leading 

 works of the English and Scandinavian chemists showing the condition of chemical 

 learning before the propagation of Lavoisier's views. A most interesting memoir on the 

 history of phlogiston is that of Rodwell, in the Philosophical Magazine, 1868, in which 

 it is shown that the idea of phlogiston dates very far back, that Basil Valentine (1894- 

 in. "i, in the Cnrsiis Tn'mii/iJtaJin A/itimonii Paracelsus (1498-1541), in his work, De 

 Rerun Xnttmt, Glauber (1604-1668), and especially John Joachim Becher (1625-1682), in 

 his Phi/Nt'cn Siiltfi-nini'd, all referred to phlogiston, but under different names. 



25 An Englishman, named Mayow, who lived a whole century before Lavoisier (in 1666), 

 understood certain phenomena of oxidation in their true aspect, but was not able to 

 develop his views with clearness, or make his doctrine a universal inheritance, or express 

 it by instructive experiments ; he, therefore, cannot be considered, like Lavoisier, as 

 the founder of contemporary chemical learning. Science is a universal heritage, and 

 therefore it is only just to give the highest honour in science, not to those who first 

 enunciate a certain truth, but to those who are first able to convince others of its 

 authenticity and establish it for the general welfare. It should be observed, with refer- 

 ence to scientific discoveries, that they are rarely made all at once, but, as a rule, the 

 first teachers do not succeed in convincing others of the truth they have discovered ; with 

 time, however, the store of materials for its demonstration increases, and other teachers 

 come forward, possessing every means for making the truth apparent to all. They are 

 rightly considered as the founders; but it must not be forgotten they are entirely indebted 

 to the labours and mass of data accumulated by many others. Such was Lavoisier, and 

 such an- all the great founders of science. They are the enunciators of all past and 

 lit learning, and their names will always be revered by posterity. 



VOL. I. C 



