STUDY OF THE VARIABLE STABS 177 



were obtained which showed well the characteristics of scores of spectra 

 on a single plate. Variable stars of long period were found to have 

 spectra in which the hydrogen lines were bright, when the variables were 

 near maximum. By taking advantage of this spectral peculiarity Mrs. 

 Fleming has been able to " pick up/ as a by-product of other investiga- 

 tions concerning stellar spectra, some 200 variables of long period. 



In 1895, the writer, while engaged in photographic work at the 

 Arequipa Station of the Harvard Observatory, began an examination 

 of photographs of the globular clusters of stars. By the use of im- 

 proved devices for controlling the motion of the telescope, satisfactory 

 photographs were obtained of the dense globular clusters. An ex- 



The Globular Cluster, to Centauri, containing 128 Variable Stars. To the naked eye 

 this cluster appears as a single hazy star of the fourth magnitude. 



animation of these led to striking results. It was found that while 

 certain clusters contained few or no variable stars, other similar 

 clusters were closely packed with them. Messier 3, a faint group, 

 barely visible as a hazy star to the naked eye, was found to contain 137 

 variables out of 900 stars examined, or about one in every seven stars. 

 This is by far the greatest proportion of variables yet found anywhere 

 in the sky. Over 500 variable stars have been found so far in dense 

 globular clusters, and, undoubtedly, these do not entirely exhaust the 

 number. 



Madame L. Ceraski, wife of the director of the astronomical ob-. 

 servatory of Moscow, has found a large number of variables by an 

 examination of photographs made by M. Blajko, of the same observa- 



VOL. LXIX. — 12. 



