34 ART. 10. X. TCITTXOITE : 



STATISTICAL RESULTS OF ALGOLS. 



(il) DISCOVETIY. 



The first star of this class of variable stars was ß Persei of 

 the second magnitude, and the two following stars added to the 

 class were not so bright. But generally speaking, the brighter 

 stars w^ere detected in the first period of the history of Algols. 

 This would be a natural consequence of the fact tliat faint stars 

 did not call us much attentions as now in the early age of the 

 science. Generally, with the development of astronomy, the 

 knowledge of this class of variable stars has also made great 

 progress, since the latter half of the last century ; but the last 

 decade especially has been noted for the increase of number. 

 We might enumerate many causes which influenced such progress 

 but the construction of the stellar map containing faint stars till 

 those of the ninth magnitude or even more fainter, as in the 

 Bonner Durchmusterung or the Cape Photographical Durch- 

 musterung and the applications of the photography into the 

 astronomical observation would be the principal causes, combined 

 with the increase of astronomers also. 



Perhaps, some considerations on the discovery of the Algol 

 might be interesting as they would show what might expect in 

 the future in general. The table below, VII, shows how the 

 number of Algols increased with time, and in it, from 1845 to 

 the present, each five years have been grouped together. The 

 first column represents the interval of time in which each group 

 extends ; the second, the number of Algols added in this interval ; 

 the third, the total number of the Algols at the end of each 

 period and the last three columns show the mean period, the 



