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THE STORY-BOOK OF SCIENCE 



irregular bands placed in tiers on the horizon at 

 sunrise or sunset. They are clouds that, in the fad- 

 ing daylight, especially in autumn, take the glowing 



tints of melted metals 

 and of flame. The 

 red stratus of the 

 morning are followed 

 by rain or wind. 

 stratus "Finally, we give 



the name ' nimbus' to a mass of dark clouds of a uni- 

 form gray, so crowded together that it is impossible 

 to distinguish one cloud from another. These 

 clouds generally dissolve into rain. Seen from a 

 distance, they often look like broad stripes extending 

 in a straight line from heaven to earth. They are 

 trails of rain. 

 1 1 Now Emile may ask his questions. ' ' 



