208 CARNEGIE INSTITUTION OF WASHINGTON. 



to furnish an adequate basis of comparison with the results of other 

 observers. 



The list of relatively faint stars of very large proper motion has 

 been under observation throughout the year. Many of these stars 

 are of exceptional interest from the standpoint both of radial velocity 

 and of luminosity, some remarkably high motions in space having 

 been found among them. As a supplement to the stars in this list and 

 in the American Ephemeris, we have added to the observing program 

 a considerable number of stars of intermediate proper motion selected 

 from the catalogue of Boss. The importance of these stars lies in the 

 evidence which they furnish with regard to the dependence of velocity 

 upon absolute magnitude, and the division of the more advanced 

 types of spectrum into the giant and dwarf classes. 



Several short lists of stars have also been added to those under 

 observation. Among these are: (1) a list of Cepheid variables; (2) 

 a considerable number of the fainter Algol variables; (3) stars with 

 recent parallax determinations; (4) a few visual double stars. 



The number of photographs of spectra obtained during the year Sep- 

 tember 1, 1917, to September 1, 1918, is 1,130, distributed as follows: 



American Ephemeris stars 266 



Stars of large proper motion 234 



Stars selected from Boss's Catalogue 322 



Miscellaneous 308 



Of these photographs, 141 are of stars fainter than the eighth 

 magnitude visually, while 146 are of Nova Aquilse No. 3. 



Radial Velocities. 



The radial velocities of 160 stars have been determined during the 

 year from measurements of three or more photographs of their spectra. 

 Observations on several hundred other stars have been partially 

 completed. Some of the more interesting results for specific stars are 

 as follows: 



1. The orbit of the spectroscopic binary Boss 46 has been determined 

 from the reduction of 34 spectrograms and the results have been 

 published. The hydrogen and helium lines show a variation of 450 

 km. and the calcium lines of about 20 km. in a period of 3.5225 days. 

 The motion of the system as given by the hydrogen and helium lines 

 is — 45 km., which differs by 20 km. from that indicated by the calcium 

 lines. 



2. The star A. G. Berlin 1366 has a radial velocity of +339 km., the 

 highest constant velocity so far observed for any star. It is of interest 

 to note that the second largest velocity, —325 km., that of Lalande 

 1966, is of nearly the same amount, but negative. 



3. The spectrum of the eclipsing variable W Ursae Ma j oris has been 

 investigated at different portions of its phase. The spectrum of both 



