STUDIES OX THE VAUIABLES OF THE ALGOL-TYPE. 39 



and the duration of the eclipse does not show very wide range 

 and it is limited to 29 in the extreme case, most part of them 

 being included in the limit from three to nine. Such facts make 

 it difficult to accept the above view without further researches. 



The mean value of the period of the six stars of the Orion 

 type is 2.4 day, that of the type A is 3.3 day and that of the 

 three stars of the type F is 3.4 day. s Aurigse which is a 

 suspected Algol and of the typ 3 F-G, has very long period. 

 Therefore, although these values are increasing with the type of 

 spectrum, it is difficult to think the relation well established. The 

 ratio between the period and the duration of eclipse, as well as 

 the density of the Algol-system does not show any relation with 

 the spectrum from such poor material. 



(c) PERIOD OF ALGOLS. 



The period of the light-variation of Algol-type variables is, 

 in general, short, ranging from a half day to about ten days 

 and only a few exceptions are now known, the extreme case 

 being RZ Ophiuchi of the period 261.8 days and in s Aurigœ, 

 a sus^^ected Algol, the period is very long as it is 27.13 in 

 years. Thus, if we omit the suspected one, we can say that all 

 of 93 Algols displays a period of less than one year. 



Now let us investigate the distribution of the Algols with 

 regard to period ; counting the number of Algols in the order 

 of period, we have the following result : here the first column 

 representing the limits of period and the second, the number of 

 stars found in the limits given in the first column. 



