ClouD ^Formation* ?i 



lowy cloud would stand as the capping of an 

 invisible pillar of ascending vapor, but as it is 

 never the case that air is not moving at some 

 velocity in the upper regions, it floats away as 

 rapidly as it is formed. This peculiar kind of 

 cloud is formed in the mid-regions of the at- 

 mosphere, and it is a summer cloud as well as 

 a land cloud. Of course, it may float off over 

 the ocean and maintain its peculiar shape for 

 a certain distance, but it is rare that such a 

 cloud would ever be seen in mid-ocean or in 

 midwinter. As the warm season advances in 

 summer, and evaporation from the earth is 

 less than the rainfall, there is less and less 

 moisture in the air, when, of course, the con- 

 ditions for cloud formation, especially inland, 

 are not so favorable as in the early spring or 

 summer. Frequently there comes a time 

 when we have a long season of dry, settled 

 weather. Probably during most of the days 

 clouds will form and we think it is going to 

 rain, but before night they have vanished, and 

 the same thing is repeated the next day and 

 the next, perhaps for weeks at a time. 



The explanation is this: We have already 

 said that so long as the air remains in a uni- 

 form condition as to temperature it will ab- 

 sorb moisture in a transparent state until it 

 is filled to the measure of its capacity at a 

 given temperature. If there were no change of 

 temperature, it would not condense into cloud. 



