X PREFACE 



cesses, as they have been denominated phenomena per- 

 petually recurring in the operations of chemistry. Yet 

 erroneous as this theory certainly is, it required for its 

 formation no common talents ; it is among the most strik- 

 ing proofs of a genius for discovery, and implies nothing 

 less than accuracy of observation, and equal sagacity and 

 boldness in deducing conclusions. The necessity of some 

 body which should supply both pure air and phlogiston, 

 had never been so clearly stated, nor had this principle been 

 applied in a systematical manner, to account for the appear- 

 ances. The reader needs only to substitute water for heat, 

 and all will be conformable to the most accurate experiments 

 with which we are even yet acquainted. Had the author 

 but fortunately fixed upon another element, as it was sup- 

 posed to be, his view of chemistry would perhaps have been 

 as just as it was extensive. But what analogy led to this ? 

 and who, without the most direct experiments, would have 

 allowed himself to imagine that water was more nearly 

 allied to phlogiston than heat ? I know, indeed, that this 

 great discovery, confirmed as it has been by several philo- 

 sophers, 1 countenanced by all the phenomena which appear 

 in the least connected with it, and, with a fate very different 

 from that of most of the great advances in science, seeming 

 at once likely to meet with universal reception, without cavil 

 or contradiction, has been lately called in question. But if 

 the account of Mr. Fontana's experiments, which has lately 

 been given in a French journal (Journ. de Phys., September 

 1785), be not exceedingly defective, it is certain that they do 

 not in the smallest degree tend to invalidate the conclusions 

 of Mr. Cavendish. They only show that Mr. Lavoisier has 

 formed some opinions with too much precipitancy. 



1 Watt, Priestly, Lavoisier, even Mr. Kirwan, while lie maintains an 

 hypothesis seemingly quite inconsistent with it, seems to admit it. 



