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ASTRONOMY: R. IV. WOOD 
comparison to the brightest part of the ring than on the violet and ultra- 
violet pictures. This again suggests a mist or dust in the planet's atmos- 
sphere which scatters the shorter wave-lengths. My infra-red photo- 
graphs of landscapes have clearly demonstrated that we can obtain 
clear photographs through a blue haze by means of the spectrum region 
above 7200. In these photographs it will be remembered that the blue 
sky comes out black and the grass and foliage snow white. (See my 
Physical Optics, page 626, second edition.) 
Interesting results were obtained as well in the case of Jupiter. In 
infra-red light the belts were scarcely visible, while the violet and especi- 
ally the ultra-violet pictures showxd dark belts, of which no trace could 
be seen in pictures made wdth the yellow screen, or by eye observations 
of the planet. 
In view of the interesting results obtained with these two planets I 
hope that similar observations will be made of Mars on the occasion of 
its next near approach to the earth. I made one photograph of the 
planet in October with ultra-violet light, but the disc was too small to 
show much of interest. 
I have been aided in this work by a grant from the Gould Fund of the 
National Academy of Sciences. 
