QO 



Popular Science MoiifJily 



It is obvious that the world is fully with a horizontal reflecting telescope 

 as well worth studying in light below of fifty-six-foot focus and fourtecn- 

 red (infra-red) as in light above violet. inch aperture to ascertain what might 

 When we reach the infra-red rays we be revealed if the Moon were photo- 

 are dealing with heat rays. A glass lens graphed with ultra-violet light. While 

 will answer our purpose in this case, but there is very little difference between 

 we must use a screen or color filter which ordinary photographs of the lunar sur- 

 absorbs all of the visible and ultra-violet face and those made with ultra-violet 



light, while 

 transmitting 

 the infra-red. 



As the cam- 

 era reveals it, 

 the infra-red 

 world is as 

 startling as the 

 ultra-violet 

 world. The sky 

 appears in 

 photographs as 

 black as mid- 

 night ; foliage 

 snow whit e. 

 The shadows 

 are intensely 

 black, simply 

 because most of 

 the light comes 

 directly from 

 the sun and not 

 from the sky. 



Applied to 

 purely scientific 

 investigation 

 this utilization 

 of infra-red and 

 u 1 1 r a-v i o 1 e t 

 rays has vast 

 possibilities. I 

 have made 

 photographic 

 studies of the 

 heavenly bod- 

 ies with invisible rays, and the results 

 obtained prove convincingly that many 

 new facts can be reached in this way. 



The Moon is a dead, arid, airless 

 body which has long ceased to interest 

 most astronomers. Every one of its 

 many thousand extinct craters has been 

 plotted; its great mountain ranges have 

 all been named; and its so-called "seas" 

 and basins have been mapped. It 

 seemed impossible years ago to add 

 anything substantial to our knowledge 

 of the Moon. I made some experiments 

 at my summer home on Long Island 



Photograph taken with infra-red light. Note 



the black sky, the white trees silhouetted 



against it, and the deep shadows 



radiation alone, 

 there is enough 

 that is signifi- 

 c a n t. The 

 brightest of all 

 extinct lunar 

 craters is called 

 Aristarchus. 

 Photographed 

 with ultra-vio- 

 let rays, Aris- 

 tarchus shows 

 a dark patch 

 which is not to 

 be seen on a 

 photograph 

 made with vis- 

 ible light. I 

 made an en- 

 largement of 

 the region in 

 which this cra- 

 ter appears, 

 and it is evi- 

 dent that there 

 is in its neigh- 

 borhood a large 

 deposit of some 

 material which 

 can be revealed 

 only by ultra- 

 \' i o 1 e t rays. 

 These photo- 

 graphs of the 

 Moon prove 

 that by systematically stud>ing the lunar 

 surface with invisible rays, we may 

 some day discover what the Moon is 

 made of almost with as much certainty 

 as if we could analyze a piece of it in 

 an earthly laboratory. 



In the late autumn of last year, 

 through the courtesy of Professor Hale, 

 the great sixty-inch reflecting telescope 

 of the Mount Wilson Obscrx-atory in 

 California was placed at m\' disjiosal 

 for four nights. The instrument is the 

 largest of its kind in the world. Photo- 

 graphs of Saturn and Jupiter were made 



