into the bottom of the gigantic telescope tube, where it will play 

 its part in future astronomical research, and whence important 

 discoveries are anticipated. 



The clear aperture of the so-called 100-incli mirror is nearly 

 101 inches. The depth of the curve in the center is one and one- 

 fourth inches ; the thickness of the finished glass at the edge is 

 twelve and three-fourths inches ; and the present weight of the 

 glass is nearly 9,000 pounds — or four and a half tons. The area 

 of the 101-inch mirrored surface is 8,012 square inches — a trifle 

 over 55.6 square feet. The focal length of the mirror is 507.5 

 inches — approximately 42.3 feet. 



Dr. Walter S. Adams, Assistant Director of the Mount AMl- 

 son Solar Laboratory, and having special direction of its large 

 affairs during the frequent absence of Director Hale in the East 

 and in Europe, has been closely identified with the development 

 of the 100-inch telescope and the construction of the great ob- 

 servatory building from the first. His special line of investiga- 

 tion is stellar spectroscopy, and he hopes for important results 

 from the use of the new telescope which it is expected will reveal 

 stars in the Milky Way and in distant star clusters down to the 

 22nd magnitude. 



The large force in the Mount W'ilson Solar Observatory, the 

 people of Southern California who have a special pride in the 

 great enterprise, the attaches of all other observatories on the 

 globe, and in fact all intelligent persons interested in the achieve- 

 ments of astronomical science, will feel a sense of relief in , the 

 successful completion of the great mirror and its safe housing in 

 its permanent home on Mount \\'ilson. 



57 



