Of M. D E LUC. 43 



riie breath is the natural phenomenon which is to be explained, 

 or the fcientific experiment by which the theory which M. DE 

 Luc refufes, is approved. 



It may be proper here to obferve, that I only confider the 

 diflblving power of air with refpedl to water, in order to con- 

 traft it with the precipitation of the diflblved fubftance, when 

 the adlion or efFedl of heat has been diminithed according to 

 the theory. It no ways concerns my propofition, whether it is 

 upon the principle of diflbhition or fimple expanfion by heat, 

 that the aqueous vapour is retained in the air, or preferved in 

 a tranfparent flate. The expreffion of dilFolution befl anfwer- 

 ed my purpofe, where the faturation of the atmofphere with 

 humidity was to be exprefled ; therefore I retained it, although 

 I had declared in this Society, when my firfl paper was read 

 and converfed upon, that I did not mean in the leaft to enter 

 into that queftion which ProfefTor Rob is ON then put. In like 

 manner, it is abfolutely indifferent to the theory, whether the 

 infpired air or breath acquires its humidity by evaporation, dif- 

 folution, or chemical refolution and compofition : Therefore, 

 if this negation, with regard to the origin of water, be intended 

 by M. DE Luc as an objecSlion to my propofition, which I 

 think has no relation with that fubjeft, it would be proper he 

 fhould fhow in what refpedt that argument of his afFedts the 

 condenfation of the water contained in the breath, when that 

 breath is mixed with another portion of air. 



I NOW proceed to the fecond propofition of M. de Luc, 

 which is, That, fuppofing my hypothefis admitted, it does not 

 follow that rain happens in confequence of this caufe ; the or- 

 dinary ftate of the atmofphere being, as he alleges, too dry to 

 admit of this efFedl. Now, this may be a very good reafon 

 why it fliould not always rain, or fhould not rain in that parti- 

 cular ftate of the atmofphere which is moft ordinary; but I 

 believe it will be difficult to perfuade thofe who admit of the 

 hypothefis, that they fhould not apply this principle in the cafe 



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