32 Report 8. A. A. Advancement of .Science. 



The following table gives in a condensed form the results 

 arrived at : — 



Date. 



1780 

 1800 

 1820 

 1840 

 1860 

 1880 

 1900 



In the southern sky there is a star so similar in type to /5 Lyrae 

 that even a casual glance at the light curves of the two stars proclaims 

 their near kinship. Furthermore, this southern star, V Puppis, has like 

 fi Lvrae, been proved to be a spectroscopic binary, its period of revolu- 

 tion being synchronous with its light changes. 



The form of the light curve of either star indicates that V Puppis 

 and /3 Lyrae ai*e close binary systems, the component stars, very much 

 deformed by their mutual attractions, circling round one another prac- 

 tically in contact. 



It is beyond the province of this paper to deal with aught but the 

 acceleration in period of /3 Lyjae and V Puppis ; yet it is of more than 

 ordinary interest to note that the former system is composed of two 

 suns each of which is at least three hundred times the size and twenty 

 times the mass of our sun, while the latter system, to the eye a faint 

 fifth magnitude star, would contain and weigh many hundred suns. 



Observations made at Lovedale since 1890 indubitably prove that 

 the period of this star, like that of ^ Lyi"ae, is steadily increasing. 

 True the acceleration is very small — one-thousandth of a second every 

 revolution — but then the star makes about 250 revolutions in a year ; 

 so that annually its period increases by a quarter of a second. 



Representing the increase in the period of Y Puppis in the form of 

 a table, we have the following dates and values : — 



Date. 



1900 

 1920 

 1940 

 1960 

 1980 

 2000 



When we wish to pass from the facts of a distinct increase in 

 period in the case of at least two stars of the spectroscopic close-binary 

 class, we have presented for our judgment three possible causes, any 



