DESERT SKY AND CLOUDS 103 



clouds of the middle air region. This veil or 

 sheet-cloud might be called a twilight cloud, 

 giving out as it does its greatest splendor after 

 the sun has disappeared below the verge. It 

 then takes all colors and with singular vividness. 

 At times it will overspread the whole west as a 

 sheet of brilliant magenta, but more frequently 

 it blares with scarlet, carmine, crimson, flushing 

 up and then fading out, shifting from one color 

 to another ; and finally dying out in a beautiful 

 ashes of roses. When these clouds and all their 

 variations have faded into lilac and deep pur- 

 ples, there are still bright spots of color in the 

 upper sky where the cirri are receiving the last 

 rays of the sun. 



The cirrus with its many feathery and fleecy 

 forms is the thinnest, the highest, and the most 

 brilliant in light of all the clouds. Perhaps its 

 brilliancy is due to its being an ice-cloud. It 

 seems odd that here in the desert with so much 

 heat rising and tempering the upper air there 

 should be clouds of ice but a few miles above it. 

 The cirrus and also the higher forms of the 

 cumulo-stratus are masses of hoar-frost, spicules 

 of ice floating in the air, instead of tiny glob- 

 ules of vapor. 



There is nothing remarkable about the desert 



Cirri. 



lee-cloudt. 



