490 Inftances of partial freezing. [Book VII. 



that the. earth, or even the air, mould be fo far cooled 

 as to occafion the congelation of water into ice. This 

 fact can only be explained, by confidering that thefe 

 irnall drops of water expofe a large furface to the ac- 

 tion of the air ; and by this means evaporation, which 

 powerfully produces cold, is promoted. For the fame 

 reafon clothes hung out to dry, are frequently frozen 

 ftiff, when no ice is formed in water expofed to the 

 fame degree of cold, but in circumftances lefs favour-* 

 fble to evaporation. 



