164 



THE NATIONAL GEOGRAPHIC MAGAZINE 



Photograph from Press Illustration Service 



"THE SUPREME COURT OP THP HEAVENS" 



This hundred-inch mirror, which has just been installed at Mount Wilson Observatory, 

 California, will bring a hundred million new stars into the ken of man. Are the nebulae 

 masses of gas or are they other universes in the great sea of infinity? Are the dark spots 

 known as "coal sacks" holes in the heavens through which astronomers can peer into starless 

 space, or are they black masses of gas curtaining off from our view worlds beyond them? 

 Scores of such questions have arisen and are to be' submitted to this wonderful mirror for 

 answer. 



kettle apply as well to the sun of the day 

 and to the stars of the night. But the 

 spectroscope proves that the chemistry 

 of coal-stove and test-tube is also the 

 chemistry of sun and star. With it man 

 went 93,000,000 miles away to find the 

 helium that is in the very air we breathe 

 and that soon will give buoyancy to the 

 dirigible airships of our navy.* 



I'ir.kY FLAMES LEAPING INTO SPACE 



It is thirty years since solar promi- 

 nences, those fiery flames that shoot out 

 from the sun to distances greater than 

 that from the earth to the moon, were 

 first discovered. Formerly they could be 

 observed only during the few minutes of 



♦See "Helium — the New Balloon Gas," in 

 tin' National Geographic Magazine for May, 

 [919. 



total eclipses of the sun, and it was pos- 

 sible to study them for only fifteen min- 

 utes in a quarter of a century. Then 

 Professor Huggins found that by screen- 

 ing off the disk of the sun and widening 

 the slit of the spectroscope we may see 

 these prominences at any time. 



With the spectroheliograph it is pos- 

 sible to get pictures of the sun and these 

 prominences in the light of a single sub- 

 stance, so that the astronomer is now able 

 to study them any bright day. Think of 

 explosions so powerful that they hurl 

 material three hundred thousand miles 

 into space with a velocity of two hundred 

 miles a second! (see page 163). 



Not only does the spectroscope tell us 

 of the materials of which the sun and the 

 stars are composed, but it also tells us 

 whether a star is headed toward us or 



