President's Address. 19 



air was a powerful supporter of combustion, Mayow was 

 quite well aware of the fact that it itself would not burn. 

 All acids, he goes on to say, contain nitre-air ; sulphuric acid, 

 for example, he tells us, consists of a union of nitre-air and 

 sulphur. Several changes, such as fermentation, putrefaction, 

 and souring of wines, are, he explains, owing to the action 

 of this nitre-air. More wonderful still, he, in the face of 

 the at-that-time-much-lauded phlogiston theory, distinctly 

 taught that, during calcination, metals increase in weight, not 

 because they lose phlogiston, but because they absorb nitre- 

 air, or, as we say now in language hardly more correct, 

 because they oxidise. In fact, so much in accordance with 

 our modern theories are Mayow's statements, that if we 

 made a few trifling alterations in the names of some of 

 the substances he makes use of — such, for instance, as sub- 

 stituting the word oxygen for nitre-air — we could almost 

 imagine, as we peruse his writings, that we had before us a 

 book twenty years old instead of two hundred. A most 

 important item in Mayow's work was his recognition of the 

 part played by his nitre-air in respiration. He noticed that, 

 and he also pointed out the compound nature of the air. 

 Mayow was, in fact, far ahead of all his predecessors, and he 

 did a great deal to extend the then scanty stock of chemical 

 knowledge ; indeed there is little doubt, I think, that if the 

 works of this wonderful man had only been a little more 

 faithfully studied at the time, the world would not have 

 heard so much about phlogiston, and subsequent great chemical 

 discoveries would have been made much earlier. 



Another theory than that of Hooke, and one of a very 

 different nature, was advanced about the same time as that 

 in which Mayow had been making his famous experiments. 

 The celebrated phlogiston theory, which shed such a power- 

 ful influence on the science of chemistry, first saw the light 

 about the year 1669. This theory, which was first promul- 

 gated by John Joachim Becher, and afterwards supported, 

 and in great part altered, by George Ernest Stahl, was pro- 

 posed for the purpose of explaining various chemical pheno- 

 mena, but principally that of combustion. There can be no 

 doubt whatever that the advancement of this theory of 



