STUDIES ON THE VAETABLES OF THE ALGOL-TYPE. 



41 



days to eight days in 20 cases : thus, Algols in the longer period 

 are very rare. The lower curve in the figure is the result from 

 55 Algols when we made some investigation in 1908 ; the further 

 addition of Algols does not materially change the result as it is 

 clearly shown in the upper curve. Formerly, it was noted that 

 Algols whose periods lie between two and four days were mostly 

 prevailing, but recently the relation is somewhat changed, as the 

 number of Algols having a period less than one day have in- 

 creased : still on the whole, the characteristic point that the 

 Algol-type variable in general have a period less than four days 

 is also very remarkable. 



Next, let us examine Table II, where the Algols are arranged 

 in the order of their periods, then we shall see there is a general 

 tendency for the ratio to increase with the period. Thus, in 

 order to find the relation between these quantities, I grouped 

 together every nine stars in the order of their periods and 

 obtained eight groups, omitting the last three stars which are of 

 exceptionally longer period. In the following table, the mean 

 values of the period and ratio for each group are given in the 

 first two columns. 



TABLE X. 



