58 OP CLOUDS. CHAP. 2. 4: 



it has approached a larger one within a certain 

 distance, is forcibly and suddenly attracted to the 

 latter. When these ephemeral mountains of 

 electrified vapour have increased much, as they 

 do towards the middle of the day, large ones 

 often inosculate, and form dense and extensive 

 irregular masses. Something else besides this, 

 however, seems necessary to cause that density 

 and continuity of a base, common to several 

 superstructures which constitute cumulostratus. 



The rapid formation and disappearance of 

 small cumuli is a process constantly going on in 

 particular kinds of weather, particularly when 

 the air is clear and dry, with light Easterly 

 breezes. These little Stackenclouds seem to 

 form out of the atmosphere, and to be resolved 

 again as rapidly into it. 



On the elevation of a Fallcloud in the morning, 

 we often see cumuli forming at its upper part; 

 probably the same particles of vapour, on the 

 return of the vapour plane, take the form of the 

 cloud of day, and subside in fog again in the 

 evening See Plate II. Figs. 3, 4. 



