THE WATER VAPOR OF THE AIR 



229 



r 



A - 

 .rrl. 





FIG. 160. Cumulus Clouds. Types frequently seen in summer. Tops 

 like "A" are likely to develop showers, sometimes before long. The dark 

 spot A' is the base of "A" or of a similar top behind "A." The top "B" is 

 slightly fringed, showing that rain has begun. The rain seen at B' is probably 

 falling from cloud ".B." The rain at "C" apparently falls from another 

 cloud behind "A." 



FIG. 161. Large cumulus, partly hidden. The dark clouds across its 

 front are rather low clouds much nearer the camera. . Note the brilliantly 

 lighted top. The sharp, clean-cut outline above shows that no rain has de- 

 veloped in the portions visible. 



