312 LAVOISIEK. 



veries were made in England which call for our careful 

 observation, the composition of water and of the nit- 

 rous acid. Respecting the latter discovery there is no 

 question whatever. Mr. Cavendish alone is its author. 

 Dr. Priestley had shown that nitrous acid was resolvable 

 into nitrous gas, which he discovered, and oxygen. 

 M. Lavoisier had never gone further than to suppose 

 that gas the base of the acid. He had never suspected 

 it to be compounded of any other known materials, 

 except in so far as it plainly contained oxygen ; and 

 as for azote, the residue of atmospheric air after the 

 oxygen gas, or respirable part, is withdrawn from it r 

 we find him expressing strongly (' Mem.,' 1777,) that 

 this is a body of whose nature we are wholly ignorant. 

 I am not aware that he ever laid any claim whatever 

 to share in Mr. Cavendish's great discovery, to which 

 he was led by the most philosophical consideration of 

 the acid always found when oxygen gas, impure from 

 the presence of nitrogen or azote, is burnt with in- 

 flammable air. A careful course of experiments devised 

 and directed by him, performed by his colleagues of 

 the Royal Society, led to the knowledge of this im- 

 portant truth. 



But the other great discovery with which his name 

 is inseparably connected stands in different circum- 

 stances. Nothing can interfere with his title to be 

 regarded as having first made the capital experiment 

 upon which it rests ; but it is equally undeniable, that 

 from less elaborate experiments Mr. Watt had before 

 him drawn the inference then so startling, that it 

 required all the boldness of the philosophic character to 

 venture upon it the inference that water was not a 

 simple element, but a combination of oxygen with in- 

 flammable air, thence called hydrogen gas. That Mr. 

 "Watt first generalized the facts so as to arrive at this 

 great truth, I think, has been proved as clearly as any 

 position in the history of physical science. (* Life of 

 Watt,' Historical note in Appendix. Eloge of Watt 



