286 CLOUDS AND RAIN. \ 



is the stronger attraction of the particles of water towards j 

 the air than towards each other, those that are already dis- j 

 solved and taken up will be raised still higher, by the attrac- 

 tion of the dry air, which lies over them, and thus will dif- ' 

 fuse themselves, rising gradually higher and higher, thereby « 

 leaving the lower air not so much saturated, but that it will ] 

 still dissolve and take up fresh particles of water ; which  

 process is greatly promoted by the motion of the wind. 



When the vapours are thus raised into the higher and j 

 colder parts of the atmosphere, some of them will coalesce ; 

 into small particles, which, slightly attracting each other, : 

 and being intermixed with air, will form clouds ; and these : 

 clouds will float at different heights, according to the quan- j 

 tity of vapour borne up, and to the degree of heat in the up- \ 

 per part of the atmosphere. The clouds, therefore, are  

 generally higher in summer than in winter ; in the former \ 

 season they are from one mile to three miles high, and in 

 the latter from a quarter of a mile to a mile. j 



When the clouds are much increased by a continual ad- j 

 dition of vapours, and their panicles are driven close together " 

 by the force of the winds, they will run into drops heavy • 

 enough to fall down in rain. If the clouds are frozen be- | 

 fore their particles are gathered into drops, small pieces of ; 

 them being condensed, and made heavier by the cold, they i 

 fall down in flakes of snow. If the particles are formed into • 

 drops before they are frozen, they become hailstones. When i 

 the air is replete with vapours, and a cold breeze springs up | 

 which checks the solution of them in the air, clouds are | 

 formed in the lower parts of the atmosphere, and these com- '. 

 pose a mist ox fog : this usually happens in a cold morning ; ; 

 but the mist is dispersed when the sun has warmed the air,, \ 

 and made it capable of dissolving the watery particles of ' 

 which the mist is composed. 



Southerly winds generally bring rain, because, being J 

 commonly warm, and replete with aqueous vapours, they are ] 

 cooled by passing into a colder climate ; and therefore part | 

 with some of them, and suffer them to precipitate in rain : ' 

 northerly winds, on the contrary, being cold, and acquiring I 

 heat by coming into a warm climate, take up or dissolve I 

 more vapour than they before contained ; and ttierefore are } 

 dry and parching, and usually attended with fair weather. • 



Gregory. 



