STUDIES ON THE VARIABLES OF THE ALGOL-TYPE. Ö 



ledge of this side only for a few stars and most of them are so 

 faint that they are not suitable for the present state of spect- 

 rographs. Nevertheless, certain comparative studies on these 

 stars will be profitable, and with this hope, I ventured to do 

 some work on these variables. 



This work was begun two years ago for 5o Algols, then 

 available, and the principal results were reported to the Astro- 

 nomical Club at this observatory (Japan A. H., I, 101 : 1908). 

 The present discussions are based upon the more increased 

 material, but I found the chief results to be the same as those 

 obtained from the previous investigations. 



DEFINITIONS OF AN ALGOL. 



Strictly speaking, the variables belonging to the type of 

 Algol must be the ones which indicate the similar characteristics, 

 in the mode of variation of light, with those of the star ß 

 Persei. At first, the star was known as a star whose light, 

 though it continues a long time as constant, still in a short 

 time, declines in intensity but after it has attained its 

 minimum brightness, it soon begins to increase in light until the 

 the normal brightness is re-attained. Patient studies on ß Persei 

 declared that such change of light repeats itself periodically and 

 the light-curve is nearly symmetrical with respect to the minimum. 

 Thus, as the definition of the typical star of the variables be- 

 longing to the Algol type, we can enumerate the following 

 peculiarities. 



I. The variation of light at first begins with a sIoav diminish- 

 ing of light from the normal. Then the rate becomes 



