HENRY CAVENDISH. 435 



with sulphuric acid, the result of which he described as the 'rising 

 of the wind'; and many of Cavendish's predecessors, Boyle among 

 others, had encountered it; but Cavendish, who called the gas 'inflam- 

 mable air,' was the first to examine its properties carefully and to de- 

 scribe them.* Cavendish is also entitled to be called the discoverer of 

 the constant composition of the atmosphere, and its first accurate 

 analyst, for in 'An Account of a New Eudiometer' (1783) he showed 

 the atmosphere to be of constant composition and to consist chiefly of 

 'phlogisticated' and 'dephlogisticated air' (nitrogen and oxygen), and 

 he observed that when the electric spark passing through his eudiometer 

 caused the 'phlogisticated' and 'dephlogisticated air' to unite, there 

 was always left a small bubble which he could not get rid of in any 

 way. This small bubble we now know to have been 'argon/ In his 

 celebrated paper read before the Royal Society in 1784, on 'Experi- 

 ments on Air,' he gave an account of the discovery of the composition 

 of water and of nitric acid. He showed that nitric acid, which had been 

 known by Geber probably in the eighth century, was produced when 

 nitrogen mixed in small quantity with hydrogen was exploded by the 

 electric spark in the presence of an excess of oxygen. But strictly 

 speaking we cannot assign to him the merit of the discovery of the 

 composition of nitric acid, for he regarded nitric acid as a simple, or 

 at least an undecompounded body, while nitrogen, according to him, 

 was a compound. He was thus not the direct asserter of the modern 

 doctrine of the composition of nitric acid, and to Lavoisier belongs the 

 merit of the true interpretation of Cavendish's results. 



Wilson's presentation of 'A Critical Inquiry into the Claims of All 

 the Alleged Authors of the Discovery of the Composition of Water' f 

 makes it certain that Cavendish was the first consciously to convert 

 hydrogen and oxygen into water, and to teach that it consisted of them. 

 In his own words 'water consists of dephlogisticated air united with 

 phlogiston,' and as dephlogisticated air was his term for oxygen and 

 phlogiston his term for hydrogen, this statement corresponds closely 

 with the modern view of the nature of water. His inheritance of the 

 prejudices of the early phlogiston school led him to the erroneous 

 conclusion that every combustible contains hydrogen, and that the 

 deoxidation of air and the oxidation of combustibles are invariably 

 accompanied by the production of water. The discoverer of so great a 

 truth as the composition of water may be forgiven for .overestimating 

 its importance. 



While his experiments on the composition of water were made in 

 the summer of 1781, his paper, 'Experiments on Air/ was not read 



* Lavoisier named the gas 'hydrogen,' i. e., water-former. 

 t In the 'Life and Works of Cavendish,' by Dr. G. Wilson, published for the 

 Cavendish Society, London, in 1851. 



