28 CARNEGIE INSTITUTION OF WASHINGTON. 



report for the past year has been prepard by Mr. Walter S. Adams, now 

 Acting Director of the Observatory. 



The work of this establishment is now so extensiv and so varid that it is 

 somewhat difficult to summarize even in its salient aspects. In addition to 

 the observatory proper, with its four principal telescopes and much auxil- 

 iary equipment on Mount Wilson, there are the physical laboratory and the 

 instrument shops at Pasadena, along with special divisions devoted to the 

 work of computations and construction respectivly. To become conversant, 

 therefore, with the complexity of activities of this department, one must read 

 the somewhat lengthy but relativly condenst annual reports of the Director. 



By way of equipment several large pieces of apparatus for the new tower 

 telescope, for the 6o-inch telescope, and for the 100-inch grinding machine 

 have been made at the shops. The towers for the new 150- foot tower 

 telescope, begun a year ago, are now finisht along with the well, 75 feet 

 deep in the rock below, which forms a part of the telescope tube of this 

 novel instrument, now essentially complete except for its spectroscopic 

 attachments still under construction at the shops. Some preliminary trials 

 made recently with this instrument indicate that it will fulfil the sanguin ex- 

 pectations entertaind in respect to its capacity. 



At the time of the annual meeting of the Board of Trustees a year ago 

 "The Monastery," a wooden building on Mount Wilson supplying quarters 

 for the resident members of the observatory staff, was completely destroyd, 

 along with a considerable number of books and other valuable property, by 

 fire. This building has been replaced during the year in somewhat enlarged 

 form by a reinforced concrete structure. 



Progress has been made during the year in the details of designs for the 

 proposed 100-inchor "Hooker" telescope, for which Mr. J. D. Hooker, of 

 Los Angeles, made a substantial gift to the observatory some years ago. 

 This work has been in charge of Professor Ritchey, whose construction of 

 the 60-inch reflector has provd so signally successful. After repeated trials 

 and failures to make a satisfactory disk the contracting firm at St. Gobain, 

 France, have quite recently renewd the hope that a disk they now have an- 

 nealing may meet the exacting requirements set by the astronomers. 



Allusion has alredy been made in an erlier part of this report to the meet- 

 ing of the International Union for Cooperation in Solar Research held at 

 the observatory during the week of August 29 to September 4 of the cur- 

 rent year. An outline of the proceedings of this meeting, which was of 

 peculiar interest to the observatory staff, is given by the Acting Director at 

 the end of his report. In spite of the difficulties of access to the observatory 

 site, this meeting was regarded as the most important held by the Union. 

 Opportunities were afforded the visiting astronomers and physicists to 

 inspect the entire establishment and to test especially the efficiency of the 



