CAVENDISH. 99 



have separated them from each other. But it was 

 also quite possible that the iron gave out hydrogen, 

 and that the hot water was partly kept in solution 

 by this gas, partly combined with the iron, for on that 

 supposition the combined weight of the calcined iron 

 and the hydrogen gas would be exactly equal to the 

 united weight of the water evaporated, and of the iron 

 before calcination. The previous discovery of Watt 

 and Cavendish is liable to no such ambiguity ; and it 

 has the merit of also removing all ambiguity from the 

 experiment of Lavoisier, which it manifestly suggested. 



These great discoveries placed Cavendish in the 

 highest rank of philosophers. No one doubted of 

 nitrous acid ; that he was the undisputed discoverer of 

 the composition of water, before Mr. Watt's claim, is 

 equally certain ; nor, even now, is it necessary for the 

 defenders of Watt's priority to deny that Cavendish 

 made the great step without any previous knowlege 

 of Watt's reasoning, while all admit that his experi- 

 mentum crucis was of the greatest value in completing 

 the foundation on which Watt's happy inference had 

 been built. Lavoisier's attempt to intrude himself was 

 wholly unsuccessful ; it had no effect whatever except 

 to tarnish his reputation, already injured sufficiently 

 by his similar attempt to share in the discovery of 

 oxygen. All men held Cavendish as placed among 

 the greatest discoverers of any age, and only lamented 

 that he did not pursue his brilliant career with more 

 activity, so as to augment still farther the debt of gra- 

 titude under which he had laid the scientific world. 



The reader, especially the French reader, must not 

 suppose that any prejudice respecting Lavoisier has 

 dictated the remarks occasionally made in the course 

 of this work upon his pretensions as a discoverer. It 

 is scarcely possible to estimate too highly the services 

 which he rendered to chemical science by his labours. 

 The truly philosophic spirit which guided his researches 

 had not been found to prevail much before his time in 



