02 OF CLOUDS. CHAP. 2. 7. 



is changed for a more obscure and grey colour. 

 This may be only the effect of the interposed 

 water of the falling Rain ; but if not, and if the 

 nimbus be effected by an intense union of the 

 watery particles, as I at present believe, the 

 intense blackness of the previous cumulostratus 

 must depend on some other principle. The 

 mountains of this cloud, and its different ap- 

 pearances are mentioned in another place. 



SECTION VII. 



Of Nimbi which result from the visible Coales- 

 cence of distinct Clouds. 



AN artificial division may be made of nimbi 

 into three kinds. Firstly ; those which result 

 from the visible coalescence of distinct clouds. 

 Secondly; those which. follow the interfusion of 

 moisture between distinct clouds : and, thirdly ; 

 those which appear to form spontaneously in 

 the air, without the precurrence of either of 

 the above phaenomena. All these may, I think, 

 be explained on the principle of the union of 

 the differently electrified particles of which the 

 clouds are composed. 



