LIFE cf Dr IIUl-tOK 63 



firfl law, the temperature, the humidity, and the power of con- 

 taining humidity, in the mixture, being all arithmetical means 

 between the lame quantities, as they exifted previoufly to the 

 mixture, the temperature produced would be exadly that which 

 was required by the humidity to preferve it In its invifible 

 form. If the fecond law took place, the moifture adlually con- 

 tained in the mixture would be lefs than the temperature was 

 capable of fupporting ; fo that inftead of a condenfatlon of hu- 

 midity, the air would become drier than before. 



If, on the other hand, the third law be that which takes 

 place, after the mixture of two portions of air of different tem- 

 peratures, the humidity will be greater than the temperature is 

 able to maintain, and therefore a condenfatlon of it will follow. 

 Now, the experience of every day proves, that the mixture of 

 two portions of humid air of unequal temperatures, does indeed 

 produce a condenfatlon of moifture, and therefore we are autho- 

 rifed to conclude that the laft-mentioned law is that which adu- 

 ally prevails *. 



^ It is obvious that this principle affords an explanation of the 

 formation of clouds In the atmofphere, and that currents of air 



Vol. v.— P, XII. i 



. . * or 



•It has been fuppofed that the chemical folutlon of humidity in air is necef- 

 fanly .mp hed m this theory of rain. The truth is, that the air is here con- 

 fidered only as the vehicle of the vapour, and that the tranfparent ftate of the 

 kner as fuppofed to depend on the temperature, or the quantity of heat; but 

 whether that heat ad on the vapour folely and direftly, or indireaiy; by increa- 

 mg.the power of the air to retain it in folution, i.. with refped to this theory al- 

 together immaterial. ■'' 



^ Da HuTTON has indeed ufed the common language concerning the folution of 

 humiduy ,n_ a^ ; but the fuppofition of fuch folution is not effential to his theory 

 He feemed, indeed, to entertain doubts about the reality of that operation, found- 

 ed on the circumftance of evaporation taking place ^n .acuo. Experiments made 

 by M Dalton iince the death of Dr Huttc, ihew that there is great reafon for 

 fuppohngthat the air has no chemical aftion whatever on the aqueous vapour 

 contained mit. Manchejier Memoirs, -fol.^.-^. x,'>^%. ^ 



