78 Cincinnati Society of Natural History. 



These questions suggest their own answers, or rather the various 

 theories which have been put forth to account for the phenomena 

 observed. It is manifest that in attempting to grapple with this 

 subject, we are questioning the very nature and constitution of 

 those distant worlds, involving not only the mechanical structure of 

 their systems, but the cosmical forces which brought them into 

 being. 



Prof. Newcomb, of the Washington Observatory, believes that 

 the variability of many stars can be accounted for by supposing 

 them to be suns like our own, and subject to similar sun-spot dis- 

 turbances ; only on a larger scale. It is a well established fact 

 that our sun has what is called a sun spot maximum, which recurs 

 once in about eleven years, at which time its surface is often mot- 

 tled with large spots. 



Now, if these spots were large enough to measurably affect the 

 sun's brilliancy, that luminary would exhibit the phenomena of a 

 variable star to an observer in Sirius or any other sidereal orb - its 

 period being eleven years. 



Or, let us suppose our sun were to have a single spot, ten times 

 larger than any that has ever appeared on its surface, and that spot 

 should persistently remain for one year. Then, as the sun rotates 

 on its axis in twenty-five days, the distant observer would see a 

 variable star with a period of twenty-five days. But I have cited 

 instances where the well-defined period of the variable star is but 

 little more than one day. Now it would be a violent assumption to 

 suppose that a great globe like our sun, much larger than the entire 

 orbit of the moon, could rotate on its axis with that velocity — equal 

 to about a hundred thousand miles per hour for objects on its 

 equator. 



Then again the spots on our sun do not remain permanent. 

 They are visible but a few days, or at longest but a few weeks or 

 months, and are constantly changing in outlines, dimensions and 

 position. It is true that there is a certain periodicity in their abund- 

 ance, and they sometimes cover the sun's surface to such an extent 

 as to diminish the amount of light and heat given out to the sur- 

 rounding planets if measured with a sensitive scientific instrument, 

 but wholly insufficient to be noticeable at the distance of the nearest 

 fixed star. 



And it is certainly difficult to imagine a state of things where 

 one side of the sun's surface would be glowing with present solar 



