32 



GENERAL SCIENCE 



the center of the group, and more delicate and wispy on its edges. 

 They are very frequently arranged in lines in one or two directions. 



When a heavy cloud comes up in the southwest, and seems to settle back 

 again, look out for a storm. 



Clouds upon hill, if rising, do not bring rain; if falling, rain follows. 



KL 



FIG. 22. Alto-stratus. 



Alto-stratus. 3 to 5 miles high. With patches of Fracto- 

 nimbus. Thick veil of gray or bluish color exhibiting in the vicinity 

 of the sun and moon a brighter portion. They may produce 

 coronae without producing halos. 



Alto-stratus shows gradual transitions to cirro-stratus. Fracto-nimbus 

 is more popularly known as Scud, and consists of small portions of cloud at 

 a very low level which travel at some speed. 



VARIETIES AND SPEED OF CLOUDS 



