LECTURE II.] HISTORY OF CHEMISTRY. 21 



The characteristic which distinguishes his researches from 

 those of most of the other chemists of his time, is the sys- 

 tematic consideration of the quantitative relations, which con- 

 stitutes, in his hands, a decisive criterion with respect to 

 phenomena. Before Lavoisier's time and I recall this in- 

 tentionally Rey, 10 and after him, Hooke n and Mayow, had 

 turned their attention to the increase in weight on combustion. 

 The views which they stated, come very close to the correct 

 explanation of the process Mayow approaching nearest to 

 the truth. In Mayow's opinion the real substance which 

 affects combustion is the " nitro-aerial spirit " which is present 

 in the air and unites with the metal during calcination. (The 

 name of this substance is intended to recall its occurrence 

 both in nitre and in the air.) For any process of combustion 

 there are requisite, according to him, not only inflammable 

 particles (which he designates " sulphureous particles "), but 

 also the presence of this nitro-aerial spirit, the taking up of 

 which explains the increase in weight. 12 The establishment 

 of the phlogiston theory, which occurred at this period, and the 

 acceptance that it met with, show to how small an extent these 

 views were then understood, or, indeed, definitely established. 



Notwithstanding this, the priority in the mode of explaining 

 the process of combustion cannot be claimed for Lavoisier. 

 At the same time, the latter did not obtain his views from the 

 chemists above mentioned, whose works were not widely dis- 

 seminated, and were disregarded. But what places Lavoisier 

 before any of them is the fact that he not only stated, as they 

 had done, an idea which could be employed to explain some 

 phenomena, but that, with the balance in his hand, he also 

 vindicated, by means of a series of brilliant investigations, the . 

 universality of the principle of the conservation of matter. He 

 thus proved that he possessed not only a speculative head, but 

 that he was also a scientific thinker and worker, who tested his 

 views by means of intelligently conceived experiments, and, 

 from these, further created new ideas. 



10 Alembic Club Reprints, No. II. n Ibid. No. 5. la Kopp, 



Geschichte. 3, 135. 



