238 



CARNEGIE INSTITUTION OF WASHINGTON. 



the wave-lengths are not sufficiently accurate to meet the requirements 

 of the radial velocity observer. This leads unavoidably to the inference 

 that the systematic differences in the radial velocities under division 

 (a) above are due in major part, if not entirely, to the adoption by 

 different observers of different wave-lengths for the same lines. A 

 discussion of the systematic differences between the radial velocities 

 as determined at the Lick and Bonn observatories shows that this is 

 true for these two observatories. 



Systematic differences in radial velocities. 



From (1) and (2) it is evident that the systematic errors K, dependent 

 upon stellar spectral type, will require revision. At present it is not 

 feasible to separate the portion of the K-term that is due to the use 

 of erroneous wave-lengths from the portion that may be due to causes 

 within the stars themselves. In another connection Dr. Albrecht has 

 been engaged in the determination of standards of wave-length for each 

 stellar spectral type. When these are completed it will be possible to 

 attempt the separation referred to. 



OBSERVATIONS. 



As heretofore, each observer, together with a microscope reader, has 

 been on duty for a week at a time. There were IIG nights on which 

 observations could be taken, the total number of observations amount- 

 ing to 16,678. The observations were divided among the observers as 

 follows: S. Albrecht, 3,999; B. Boss, 330; A. J. Roy, 6,838; W. B. 

 Varnum, 5,511. The circle-readings for zenith distance have been dis- 

 tributed as follows: S. B. Grant, 6,141; A. R. Guy, 256; H. Jenkins, 

 4,808; H. Raymond, 5,473. Following the notation used in previous 

 reports, the observations were distributed AE 5,443, AW 4,849, BE 

 3,347, BW 3,039. Some portions of the observing list are nearly com- 

 pleted as far as the miscellaneous stars are concerned, but two cloudy 

 winters have interfered with that portion of the program. Special 

 efforts will be made to bring up the arrears. 



The observing list has been slightly enlarged, consistently with the 

 original plan, by the addition of stars shown by the Greenwich Cata- 

 logue of 1900 to have a centennial proper-motion of 10" or more. A 

 few stars have been added from other sources. 



