MOUNT WILSON OBSERVATORY^^J^ ^^^ 

 By Williams H. Knight. Qahurn 



On the summit of Mount Wilson, 6,000 feet above sea-level, and 

 two-thirds of that altitude above the dust and fogs of the populous 

 valleys below, in the clear skies and balmy atmosphere of Southern 

 California, are planted five unique and powerful instruments. 



The first instrument installed was the horizontal Snow telescope 

 which reflects the image of the sun on every clear day, through a 

 focal distance of 60 feet, producing an object full of surprising detail, 

 seven inches in diameter. The next instrument projected was a tower 

 telescope 65 feet in height, from the stationary top of which the 

 light of the sun was reflected downward, forming a solar image in 

 the observer's station at the surface of the ground. So successful 

 was this experiment in solar study that another tower telescope was 

 erected in its vicinity 180 feet in height, so constructed as to give a 

 solar image 16 inches in diameter in a laboratory which with its 

 adjuncts, extends to a depth of 75 feet below the surface of the 

 ground, where the temperature is uniform. The wonderful image 

 thus produced shows with marvelous detail, the seething, swirling 

 motions of the various chemical elements in the sun's atmosphere. 

 The rushing maelstrom of downward currents, and the upward 

 thrust of red prominences seen projecting far beyond the shadow of 

 the moon in total solar eclipses, are vividly shown in full sunlight 

 by the spectroheliograph. 



But all of these instruments were invented, designed and con- 

 structed for the purpose of studying the constitution of- the sun, the 

 nearest star in the sidereal universe. A great reflecting telescope 60 

 inches in diameter was also deemed essential for supplementing the 

 original investigations being carried on by the solar telescopes. Its 

 purpose was to make a systematic study of the myriads of other suns 

 in the universe, to ascertain in what respects they resembled or dif- 

 fered from the mighty luminary at the center of our own solar system. 



The work accomplished with this large telescope fully met ex- 

 pectations. It has thrown much light on the nature of spiral nebulae, 

 it has demonstrated the great size and enormous distance of the 

 globular star clusters, and contributed in scores of other ways to our 

 knowledge of the stars. We eagerly await what is yet to be dis- 

 closed among the deep mysteries of the universe by this telescope. 



Finally we come to that Brobdingnagian instrument, the great 

 Hooker 100-inch reflector, but recently installed in the 100-foot ob- 

 servatory, provided with every possible facility for accurate adjust- 

 ment, for delicate handling, and for convenient observing. Touch 

 an electric button and the massive dome, whose top is 100 feet above 

 the ground, mioves at will. Another button opens a shutter 20 feet 

 wide through which you peer at any object in the universe which 

 may become visible in the magic glass. Another button raises or 

 depresses the platform on which the chair of the observer is located, 



