232 CARNEGIE INSTITUTION OF WASHINGTON, 



pressions for these regions the absolute magnitude is obtained. The 

 method has been applied to the stars of several moving clusters, with 

 results for parallax in good agreement with previous determinations. 



The "cyanogen" bands have also been found to show marked in- 

 crease of absorption in the more luminous stars, thus affording another 

 measure of absolute magnitude. The effect is greatest for stars of 

 types G5 — K2 and decreases considerably toward GO and Ma. Giants 

 and dwarfs as faint as apparent magnitude 13.5 may be distinguished 

 on slitless spectrograms by this method (p. 271). 



Mention should be made of two important pieces of work, not done 

 under the direct auspices of the Observatory. One of these is the repe- 

 tition on Mount Wilson of the Michelson-Morley experiment by Pro- 

 fessor Dayton C. Miller, of the Case School of Applied Science. This 

 fundamental investigation, which should show whether increase in 

 altitude above sea-level has any appreciable effect on the perception 

 of possible relative motion of the earth and the ether, is still in the pre- 

 liminary stage and will be continued by Professor Miller. The second 

 is the initiation by Dr. H. 0. Wood of the seismological work in 

 Southern California which is being organized by the Carnegie Insti- 

 tution of Washington. In both cases the Observatory has been able to 

 assist in various ways. 



For many years visitors have been admitted daily to the Observatory 

 museum of astronomical and physical photographs on Mount Wilson, 

 and certain of the instruments have been shown by ]\Ir. W. P. Hoge, 

 the assistant in charge. During the past year about 10,000 visitors 

 have seen the 100-inch telescope. We have long hoped to arrange 

 for an open night, on which celestial objects could be shown to the 

 public with one of the large telescopes. In view of the great height 

 and small capacity of the observing platforms of the 100-inch telescope 

 it is clearly unsafe to permit their use b^^ the public. The Cassegrain 

 focus of the 60-inch telescope is easily accessible, however, and this 

 instrument has accordingly been arranged for use by the public on 

 Friday evenings. Tickets are issued without charge to those who send 

 their requests to the office of the Observatory in Pasadena. 



