The Weather 



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their heaped-up form like billows of smoke or steam, are called 

 cumulus clouds. They have various forms and sometimes 

 combine with other cloud forms. With low area centers they 



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FIG. 11. Graphic representation of the chief weather features of a cyclonic 

 area. Based upon the weather map of December 26, 1915. 



are usually in layer or stratus form, and dark in color. As the 

 warm, moisture-laden air sweeping in from the east or southeast 

 is lifted upward by the cold currents from the north, the cumulo- 



