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tion relied ? who detected and proved the composition of water, and 

 deduced the train of corollaries which flowed from it ? the answer is, 

 Cavendish. The discovery was not one of those which was within every 

 man's reach, especially in an age of loose experiment and inconclusive 

 reasoning : it was one which could never have been made, but by a strict 

 appreciation of quantities, and a careful elimination of the sources of 

 error : it formed part of the solution of the difficult problem, which at 

 that time occupied the attention of all the chemists in Europe — the 

 cause of the diminution of atmospheric air, in six several cases — in the 

 passage through it of the electric spark, in its burning with hydrogen, in 

 its contact with nitrous gas, in respiration, in the inflammation of phos- 

 phorus and sulphur, and in the calcination of metals. These phasno- 

 mena had been accounted for by a supposed phlogistication of the air, 

 and a consequent formation and absorption of carbonic acid ; Lavoisier 

 stood alone in attributing the phsenomena of the four last classes to 

 their true cause. When Cavendish took up the problem, he began by 

 proving that no carbonic acid was necessarily produced in any of these 

 processes : and then. Gentlemen, he turned to use a well-timed but in- 

 correct experiment of an inhabitant of this town, (Mr. Warltire,) and 

 he made it the basis of a series of analytic and synthetic researches, 

 unequalled then, and never since surpassed, by which he demonstrated, 

 as a means of arriving at the solution of his problem, — 1st, The quan- 

 titive composition of the atmosphere ; 2nd, The combination of hy- 

 drogen with oxygen and the quantitive composition of water; 3rd, 

 The chemical union of nitrogen with oxygen and the constitution of 

 nitric acid. From these experimental data he deduced the true causes 

 of the diminution of the air in the burning of hydrogen, and in the 

 passage of the electric spark ; he adopted Lavoisier's conclusion re- 

 specting the burning of metals and other inflammable matters, gave 

 the true account of the composition of the nitrates of potash and 

 mercury, explained the constitution of vegetable substances, and the 

 origin of the oxygen which they exhale, and finally corrected the pre- 

 mature generalization which had led the French philosopher to con- 

 sider that gas as the principle of acidity. 



Such, Gentlemen, were the splendid results of this investigation, such 

 the reinforcement which Cavendish brought to the nascent reformation 

 of chemistry. Equally worthy of observation were the means employ- 

 ed to obtain them. The experiment to be made was the combustion 

 of hydrogen with common air ; or, as it proved, its combination with 

 the proportion of oxygen which the common air contained. Now this 

 latter was then a quantity imperfectly known. Hence those analyses 



