84 THEORT of R 



eloudinefs in the atmofphere ; and this is fufEcient for deter- 

 mining the queftion, whether or not the condenfation of aque- 

 ous vapour be prevalent in the climate of this ifland ? 



8. CLOUDINESS in the fky being a demonftration of aque- 

 ous condenfation in the atmofphere, in like manner as is the 

 cafe with rain, this appearance may now be examined with re- 

 gard to- the temperature of the air, in relation to heat and cold, 

 that commonly attends on this occafion. Let us begin with 

 fummer ; and fuppofe the weather to be warm ; that is, precife- 

 ly in the natural temperature of the feafon. There is no que- 

 flion with regard to the effecl of a clear iky, or continued 

 funfhine : Heat is certainly the effecl of funfhine ; and this 

 heat is accumulated in the earth, cateris paribus, in proportion 

 to the intenfity of the light and the duration of the illumina- 

 tion. The queftion now to be examined is this, what mould 

 be the effecl of condenfation of aqueous vapour in the atmo- 

 fphere at this feafon, and in this fummer temperature ; that is 

 to fay, whether mould heat or cold be the confequence of this 

 operation ? 



NOTHING is fb eafy as the anfwer to this queftion. We fup- 

 pofe the atmofphere in the mean temperature of the fummer- 

 feafon, and that a condenfation of aqueous vapour is produced 

 by the admixture of a current of atmofphere in a different tem- 

 perature. Now, as this effecl may be produced by the admix- 

 ture of air, either hotter or colder than our atmofphere, which 

 is fuppofed to be quite ferene, the effecl muft be a change of 

 the temperature of our atmofphere, either to a greater or a lefa 

 degree of heat than its mean temperature for the feafon, accord- 

 ing as the fupervening atmofphere, producing eloudinefs in our 

 fky, mail be either hotter or colder, in its temperature, than 

 that in which we had been involved immediately before. 



FROM this conclusion, we will now draw a praclical obferva- 

 tion, which may be of fome utility in trying the theory and 

 explaining appearances. If the heat of the atmofphere be, 



at 



