l82 REPORTS ON INVESTIGATIONS AND PROJECTS. 



the character of the figure at different temperatures. So far as it is possible 

 to judge, no changes have taken place in the flaws contained in the glass 

 during the severe pressure put upon it by the process of rough grinding. 

 The disk is being figured with a ratio of focal length to aperture of 5 to i. 



While this work is being carried on in Pasadena, the French Plate Glass 

 Company is continuing at St. Gobain the attempt to cast a disk which shall 

 be free from flaws and air-bubbles. The chief difficulty encountered in re- 

 cent trials has been that of annealing in such a way as to keep the tempera- 

 ture of the entire body of glass uniform. Owing to this cause a second disk 

 cast early in this year broke in the annealing oven. In the course of their 

 experiments the St. Gobain company have succeeded in producing a flawless 

 disk 100 inches in aperture and 20 cm. thick. It is possible that in case of 

 necessity such a disk could be employed for the 100-inch telescope, provided 

 it were figured in place upon the support system with which it was to be used 

 finally. 



With the aid of a special grant from the Carnegie Institution of Washing- 

 ton the work upon the design of the mounting has been carried on actively 

 during the year. Mr. Drew has been in immediate charge, assisted during a 

 part of the year by Mr. he Grand. During the months of July and August 

 Prof. Albert Smith, of Purdue University, acted as consulting engineer upon 

 the structural design of the polar axis, tube, and building. At the present 

 time the essential features of the design have been thoroughly worked out, 

 and it should be possible to begin detailed drawings during the winter. 



Reference has already been made to some of the construction work upon 

 Mount Wilson, in connection with the plans for the erection of the loo-inch 

 telescope. This has included the grading and leveling of the site, the con- 

 struction of several small buildings for housing the machinery employed in 

 the work, and the erection of a few of the smaller piers. A large amount of 

 material for the main pier has been collected ready for use in the coming 

 summer. 



The Observatory chronicles with deep regret the death of Mr. John D. 

 Hooker at Los Angeles, May 24, 191 1. It was by the generosity of Mr. 

 Hooker that funds for the purchase and construction of the lOO-inch mirror 

 were provided originally. His active and intelligent interest, not only in the 

 progress of this work but in the activities of the Observatory as a whole, 

 will be missed greatly by the members of the staff. 



