268 CARNEGIE INSTITUTION OF WASHINGTON. 



importance of investigating the second question has led to the compila- 

 tion of an extensive list of stars with proper motions comparable with 

 those of stars for which the radial velocities have already been deter- 

 mined, but averaging about 2 magnitudes fainter. This list, consisting 

 of about 160 stars of magnitudes 7.5 to 9.0, now forms one of the prin- 

 cipal portions of the radial-velocity program. 



Observations have been continued throughout the year on the large 

 proper-motion stars with measured parallaxes; on numerous stars of 

 types A, F, G, K, and M with very small proper motions; and on a 

 considerable number of miscellaneous stars, including those suspected 

 of belonging to the Perseus group. 



The number of photographs obtained during the year is 810, dis- 

 tributed as follows: 



Small proper-motion stars, types A to Mc 553 



Parallax and large proper-motion stars 113 



Selected Areas 30 



Perseus group 29 



Absorption of light in space photographs 23 



Miscellaneous 62 



For a large majority of the photographs the 46 cm. camera and one 

 prism have been used. A few very faint stars have been photographed 

 with a camera of 18.3 cm. focal length, but the resultant velocities are 

 necessarily approximate. Some slight modifications have been made 

 in the spectrograph during the year. The most important of these is 

 the addition of a guiding eye-piece mounted on cross-slides below the 

 slit to enable the observer to select a star in the field of view of the 

 telescope, and thus guide during exposures on objects too faint to be 

 seen distinctly with the usual reflecting slit arrangement. 



Radial Velocities. 



A list of the radial velocities of 500 stars on which three or more 

 observations have been obtained has been prepared for publication 

 recenth'. The spectral types of these stars are as follows: 



B 93 F 38 K 88 



A 140 G 96 M 45 



The B and A type stars in this list were selected mainly for the 

 purpose of providing the data for a more accurate determination of 

 the elements of the two star-streams, and the results will be used for 

 this object in a future discussion by Professor Kapteyn, The F to M 

 type stars are made up of two classes: stars of large proper motion 

 and in most cases of measured parallax, and stars of exceptionally 

 small proper motion and hence of great average distance. A compari- 

 son of the radial velocities, corrected for the sun's motion, of the small 

 and the large proper-motion stars shows a rapid increase in velocity 

 with proper motion for the F, G, and M stars, and probably a corre- 

 sponding increase for the B and A stars, although large proper motions 



