30^ HYGROLOGY, AND ITS CONNECTION WITH METEOROLOGY. 



the modern whole of this work was intended to prove, how erroneous was 

 rnTstry h erro- ^^'^ iTJodern theory of chemistry, the foundation of which is to 

 aeons. suppose, that 7vater is a compound of ^m^o substances, called by- 



its authors hidrogen and'o^i^ew, and that the atmosphere is 

 principally composed of two Jiuids called by them hidroge?i air 

 and oxigen air ; a system in which, for the explanation of tlie 

 greatest atmospheric phenomena, which ought to have been 

 their firsr objects of comparison, those of clouds and rain, they 

 had been reduced to suppose a condensation of the aqueous va- 

 pour by cold, which supposition the above experiments prove to 

 be absolutely erroneous. This is the only point, wdiich I have 

 here considered j and indeed it is sufficient to overturn the 

 whole theory : but in other parts of the v/ork I entered into the 

 examination of all its parts, beginning with the original experi- 

 ments from which the coviposition of luater had been concluded 5 

 and in analysing these experiments I made it manifest, that, far 

 from being satisfactory, there were many unwarrantable hypo- 

 theses to be made, in order to connect ihe fads with the conclu- 

 •shin. 

 jBertholIet'f at- ^8. When my work had been published at Paris, Mr. Ber- 

 temptto de- thollet, one of the authors of that chemical theory, attempt- 

 ed, in the Annales de Chimie, and in another French Journal, 

 to defend the only resource of that theory, namely, that rain 

 was the effect of the condensation by cold of the aqueous va^ 

 pour existing in the atmosphere. He acknowledged however 

 two points, first, that my experiments with respect to the effects 

 of evaporated water on the hygrometer at different temperatures 

 had been made with an uncommon accuracy ; and that I had 

 thus demonstrated the errour of those, who attributed evapora- 

 tion to a dissolution of water by air. These were two impor- 

 tant concessions ; but being loth to abandon his theory, and 

 totally unacquainted with meteorological pbaenoraena, he at- 

 tempted again, as it was absolutely necessary for the support of 

 bis theory, to explain rain by the cold condensating the aqueous 

 vapour in the atmosphere ; thinking that by transporting the 

 condensation io very high regions of the air, no objection could 

 be made from immediate facts : but he was mistaken j since Mr. 

 <de Saussure and myself had proved, from immediate facts, that 

 the upper regions of the atmosphere are dryer than those that 

 we can attain. 



29. I 



