NATURAL AND PHYSICAL SCIENCE, 1700-1800 309 



air, the resulting substances weigh more than did the metal ; and 

 that if burnt in a closed space the loss in weight of the air equals the 

 gain in weight of the metal. And when, finally, he reversed the 

 experiment, decomposing the red powder of burnt mercury as 

 Priestley had done, and weighing as before, he found that the loss 

 of weight of the red powder at the end was exactly equal to the 

 weight of the " dephlogisticated air" driven off. 



Lavoisier named the gas thus derived oxygen (acid producer), 

 because its compounds seemed to him to be chiefly acids. And 

 since Black's "fixed air" was Bergmann's "aerial acid," and could 

 be made by burning charcoal in air, Lavoisier suspected that 

 fixed air contained oxygen as well as carbon. Accordingly, he 

 proceeded to burn charcoal in pure oxygen, and obtained fixed 

 air or aerial acid, which he thereupon analyzed, proving that 

 100 parts contained 72 of oxygen and 28 of carbon. He there- 

 fore named it carbonic acid. Afterward, by burning a diamond 

 in pure oxygen and obtaining carbonic acid, he proved that one of 

 the precious "stones" is really a form of carbon. Priestley died 

 clinging to the phlogiston theory, but his dephlogisticated air 

 had now become Lavoisier's oxygen. Lavoisier, one of the most 

 brilliant men of science in any age, continued as long as he lived 

 to do remarkable work. He repeated with more precision the 

 experiment of Cavendish on the synthesis of water from inflam- 

 mable air and ordinary air (or oxygen), and named the former 

 hydrogen (water producer). But, unfortunately for science, 

 Lavoisier, since he had held government office as a farmer-gen- 

 eral, found no favor in the eyes of the leaders of the French 

 Revolution and on May 18, 1794, at the age of 51, he was guil- 

 lotined. Thus was the end of the eighteenth century, otherwise 

 in most respects favorable to science and other learning, dis- 

 graced by a foul blot on civilization, as had been the end of the 

 sixteenth by the burning of Giordano Bruno ; the latter a victim to 

 misdirected religious conservatism, Lavoisier to equally misdirected 

 political radicalism. 



THE SYNTHESIS OF WATER. In 1784 Cavendish added to his 

 other brilliant discoveries that of the composition of water. He 



