62 REPORTS ON INVESTIGATIONS AND PROJECTS. 



possibility that agencies other than mere change of temperature are con- 

 cerned is not entirely excluded, but the present indications are favorable 

 to the view that the assumption of a low^er temperature will prove to be 

 the simplest means of accounting for the phenomena. This view is based 

 not merely upon an extensive series of laboratory experiments, but upon 

 various other criteria, one of the most important of which is the fact 

 discovered in the course of our recent investigations, that spectroscopic 

 phenomena resembling in the closest degree those observed in sun-spots 

 are apparently characteristic of certain stars which in all schemes of stel- 

 lar evolution are classified as cooler than the sun. This fact is of special 

 significance in its bearing upon the broader applications of our sun-spot 

 investigations. It illustrates the truth that the correlated study of solar, 

 stellar, and laboratory phenomena ofifers a most promising means of 

 attacking the problem of stellar evolution. It is now evident that the 

 investigations we have begun on the spectra of sun-spots, and partially 

 interpreted through laboratory experiments, are likely to serve as our 

 surest guide in those more general investigations of stellar phenomena 

 which it is our prime object to undertake. 



Of the other events of the year, which are discussed more specifically 

 in the body of this report, certain ones call for general comment here. 

 The destructive earthquake of April i8, from which our colleagues of the 

 Lick Observatory so fortunately escaped, naturally raised apprehensions 

 as to the fate of the mounting of our 6o-inch reflector, then approaching 

 completion at the Union Iron Works in San Francisco. It was some time 

 before definite knowledge of the facts could be ascertained. It was then 

 learned that, although the Union Iron Works were outside of the great 

 fire zone, the direct efifects of the earthquake shock within their grounds 

 were very serious. Nevertheless, the reflector mounting wholly escaped 

 injury, though by the barest of margins. The heavy labors of reconstruc- 

 tion, together with subsequent strikes, interfered so seriously with the 

 completion of the mounting that it has only recently been delivered to 

 us in Pasadena. It is now being erected, and the extensive work to be 

 done upon it by our machinists will occupy them for fully a year. It is 

 our hope that this work may be completed in time to permit the telescope 

 to be set up on Mount Wilson in the autumn of 1907. The polishing 

 of the mirror, like all of the other important work of the optical and 

 instrument shops, has proceeded most satisfactorily under Mr. Ritchey's 

 direction. At the present time the figure of the mirror has reached a 

 high degree of perfection, but it will be still further improved before it is 

 regarded as satisfactory. 



Thanks to the assistance and cooperation of President Woodward, the 

 long-standing problem of a road up Mount Wilson has at last been satis- 



