Page:Popular Science Monthly Volume 59.djvu/445

Rh 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 'inflammable air,' was the first to examine its properties carefully and to describe 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 'Experiments 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' 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