1922.] The Ninth Indian Science Congress. IS.C. 43 
telescope had measured the radial velocities of a few stars and 
some planetary Nebulae. The first reliable measures of radial 
velocities were obtained in 1890 by Vogel and Scheiner of 
Potsdam by photographic methods. The subject has, since 
been taken up at a number of observatories, the most impor- 
in the case of B type stars to about 5 Km. per — Sag 
ably due to pressure effect in the extensive atmospheres : 
such stars. ‘The radial velocities of a considerable number o 
faint stars have been observed at- Mount Wilson, and ne 
Royal Observatory at the Cape has also published some exce 
ent measures. 
A consideration of the proper motions of a few stars om 
not fail to convince Herschel that a part of the motions mus 
simple graphical process he deduc 
motion from the proper motions of o 
