4 ART. 19. N. ICHINOHE : 



more rapid and finally losing the rate of variation, it 

 attains to the minimum after the gradual decrease of 

 light. Then, in nearly reversed order, the light increases 

 till tlie maximum is attained. 



II. Such variation of light is periodical and in only a small 

 portion of the period, the light changes gradually and 

 during the remaining interval, it keeps the normal 

 hrightness. 



But these definitions are not strictly satisfied actually for 

 all the Algols. Thus, when we study Algol stars, it is of the 

 first importance to define these stars under the admissible modi- 

 fications. In order to so amend the definitions that all the 

 Algols, ordinarily taken in this class, will be included, it will be 

 necessary to consider what are the points that must be changed. 

 I. The period is not strictly constant but it is subdued by 

 some variations whose laws are unknown or known in 

 part only. 

 II. The diminution of light takes place generally in only a 

 small part of the j)eriod and the ratio (P/d) between the 

 whole period (P) and the duration of the change of 

 light (d) is included between certain limits. 



III. In some Algols, the minimum brightness is not constant. 



IV. The decreasing and increasing branches are symmetrical 

 in some of them ; nearly symmetrical in others ; w^hile 

 they differ pretty considerably in others. 



V. In some Algols, there is a secondary minimum between 

 the two successive principal minima. 

 Now, let us suppose that it is permitted to allow these 

 modifications without limit, then the so-called Algols will disap- 

 pear from the variables as classified. Here it would seem pro- 



