President's Address. 25 



name of Cavendish is inseparably connected is, of course, liis 

 discovery of the composition of water. His researches, how- 

 ever, upon hydrogen, or inflammable air as he called it, were 

 very important and interesting. This inflammable air of his 

 he obtained by the action of dilute acid upon certain metals, 

 such as iron, zinc, and tin ; and as showing the perfect way in 

 which he carried on his experiments, I should mention that 

 he clearly determined that the air given off from each metal 

 was the same both in quantity and quality, no matter in what 

 proportion he added the acid so long as the same amount of 

 metal was employed. Cavendish also made a series of ex- 

 periments by acting on the metals just named with acids of 

 different degrees of concentration. Thus he found that with 

 strong nitric acid the effect, to a certain extent, was the same 

 as with, say, dilute sulphuric acid, viz., that gas was generated. 

 He found, however, that the result was so far different, that 

 while in the case of dilute acid the gas which was given off 

 was inflammable, in the case of the strong nitric acid the gas 

 which was evolved was not inflammable. He also made ex- 

 periments in which he treated different metals with strong 

 sulphuric acid, the result of which was that what he called 

 sulphurous air was evolved. All of which are the same 

 results as wd obtain in the present day, and are described in 

 language almost identical with ours. From this we have 

 good proof that Cavendish was an accurate experimenter and 

 observer. Unfortunately in his explanations of these different 

 effects, he dragged in the phlogistic theory, in which, strange 

 as it may seem, the great Sir Henry Cavendish was a firm 

 believer. The gas which was given off when the metals were 

 dissolved in dilute sulphuric acid he regarded as phlogiston. 

 The metals, it will be remembered, were regarded by phlogis- 

 tians as compounds consisting of the calx of the metal united 

 with phlogiston. This phlogiston, therefore, as Cavendish 

 remarks, is given off alone by metals when they are treated with 

 dilute acid, but is evolved in combination with the acid when 

 the metals are treated with that in a concentrated state. If this 

 absurd phlogistic theory had never been heard of, and therefore 

 not instilled into every one who gave any attention to chemical 

 matters, as it seems to have been at one time, it is quite pos- 



