145 



has been frequently noticed by poets, in rainy and changeable 

 weather it has a light fleecy texture, and is irregular in the form 

 of its component parts, approaching to the cirro-stratus. 



The C.!.)ii:lo-!t'rnin.s, or twain-doud usually presents an hori- 

 zontal base upon which the cloud appears heaped or piled up, it 

 is of common occurrence p evious to rain, arid sojn. ti:)i'-s changes 

 into the the nimbus or rain-cloud. In our fi<rure, the cuinulo- 

 stratus is shown at the left and ni inline at the right. The eumu- 

 lo-stratus is usually formed out of !'ic cumulus, which grows 

 denser and spivails out laterally until it cveiliangs its base, while 

 the tops remainingdistinetseem like yo many snow-capped moun- 

 tains, or rocks piled up. When the curuulo-.'-t.ratus increases in 

 density and hiaekne-'a, indicating rain, the nimbus or rain-cloud 

 is formed. As soon as the actual rain commences the blackness ia 

 changed into a dark gray orshitv color. After the rain the clouds 

 separate and form again cumuli, cirri, and cirro-cumuli, which 

 float in the upper regions of the atmosphere, while the broken 

 fragments of the nimbus sail along- in the currents of wind 

 below. 



It often happens that a cloud, in descending, enters a stratum 

 of air warmer than itself and is again converted into vapor and 



