DESERT SKY AND CLOUDS 



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fact responsible for the gorgeous sunsets, the 

 tinted hazes, the Indian-summer skies, the hot 

 September glows. These all appear in their 

 splendor when the sun is near the horizon-line 

 and its beams are falling through the many 

 miles of hot, dust-laden air that lie along the 

 surface of the earth. The air at sunset after 

 a day of intense heat-radiation is usually so 

 thick that only the long and strong waves of 

 color can pass through it. The blues are al- 

 most lost, the neutral tints are missing, the 

 greens are seen but faintly. The waves of red 

 and yellow are the only ones that travel through 

 the thick air with force. And these are the 

 colors that tell us the story of the desert sunset. 

 Ordinarily the sky at evening over the desert, 

 when seen without clouds, shows the colors of 

 the spectrum beginning with red at the bottom 

 and running through the yellows, greens, and 

 blues up to the purple of the zenith. In 

 cool weather, however, this spectrum arrange- 

 ment seems swept out of existence by a broad 

 band of yellow-green that stretches half way 

 around the circle. It is a pale yellow fading 

 into a pale green, which in turn melts into a 

 pale blue. In hot weather this pallor is changed 

 to something much richer and deeper. A band 



