56 ANSWERS to the OBJECTIONS 



wherein condenfation of vapour is formed, by mixing the at- 

 mofpheric air with that which had been rarefied, or by emitting 

 into the atmofphere air which had been condenfed. In all 

 thofe cafes, there is the mixture of two portions of the atmo- 

 fphere, in fufficiently different temperatures, to produce con- 

 denfation of humidity, which actually happens. Thus, all 

 thofe appearances are properly explained by the theory, or, as 

 experiments, they confirm the aflumed proportion. 



But if thus every particular example is a proof, and if each 

 example is unexceptionable in its kind, what degree of evidence 

 mufl arife from the united teftimony of every poffible experi- 

 ment almoft which can be adduced in relation to the fubjecl ? 

 It is to be prefumed that M. de Luc, with all his extenfive 

 knowledge of nature, could not adduce one fhadow of a fadl 

 by which the alleged proportion could be called in queftion or 

 difproved. 



M. de Luc concludes in the following manner, (parag. 588.) 

 " Je ne vois done rien dans ces faits, qui contribue a eclaircir 

 " la queftion de la pluie ; et par consequent elle me paroit 

 " refler au point ou je l'avois amene avant que d'entrer dans 

 " ce nouvel examen. Je tire meme du memoire du Dr Hut- 

 " TON, ces deux confequences, qui juflifient le travail que j'ai 

 " enterpris. Quoiqu'il paroiffe s'etre beaucoup occupe des 

 " phenomenes de la pluie, aucune theorie a leur egard ne l'avoit 

 " fatisfait : et d'apres ce qui lui etoit connu des loix de l'hygro- 

 " logie, il avoit conclu, que la precipitation de l'eau Ample- 

 " ment evaporee, ne pouvoit etre produite que par refroidiffe- 

 " ment. Or, ce font, entre autres, ces deux motifs qui m'ont 

 " conduit dans mes recherehes." 



M. de Luc had no occafion to juftify his undertaking by 



any opinions of mine. His writings will always contain 



matter fufficient to intereft the public ; and his ideas of hygro- 



logy muft be fupported upon their own bottom. I therefore 



vi(h he had not given as my ideas expreflions which, however, 



in 



