2 ART. 19. N. TCHINOHE : 



discovered by Fritscli in 1821 as a variable, and more recently 

 the Algol-like nature of the light-change has been suspected by 

 Ludendorff). Eleven years later, the Algol-like variation of 

 light was again detected in o Librae by Schmidt, in 1859. 

 Thus, although in early times the variables of this class were 

 considered as rare objects, the number of them slowly increased 

 with time until recently it has increased at a great rate. Thus, 

 it became usual to call any one of them simply as an Algol. 

 At the end of the year 1900, the number of Algol-variables was 

 21 in all, but great has been our surprise when w^e learn that 

 during the last ten years the number has become quite great 

 and we could count 93 or 94 stars (omitting or including s 

 Aurigae) in this class of variables at the end of June, this year. 



Some comparative studies have already been tried by several 

 astronomers on the variables of this class ; but formerly, the 

 number of the stars was very small, as we have just said, so 

 that perhaps it would be dangerous to regard the conclusions as 

 entirely authentic. Even now, the number is yet not sufficiently 

 large to make some important investigations. When we go on 

 a step farther, we shall soon find that for many of them the 

 necessary investigations of the light-curve are not published yet 

 and this is a great obstacle to the attempt to make a compara- 

 tive study on these variables. As the cause of the variation of 

 light for some of the variables in this class was confirmed to 

 be interpositions of a dark satellite between a bright star and 

 the observer on the earth, as suggested by Goodricke, by the 

 spectroscopical investigations of the stars by Vogel and others, 

 the extention of the spectroscopic observations on all the Algols 

 is greatly to be desired for the studies of these in order to know 

 the general nature of Algols, but unfortunately we have know- 



