88 Professor Struve on Double and Triple Stars, as 



double stars of the first class are so near one another that it 

 is impossible to avoid thinking they are united is still more re- 

 markable, and I have also seen this three times. A fourth 

 case is where a double star of the first class is found at a dis- 

 tance of one minute of a degree from a third, and where the 

 four stars are of equal brightness, and of the eighth magnitude. 

 The pair No. 4 and 5 of Lyra supplies an example of a fifth 

 case; it is that of two double stars of the first class, each of 

 the fifth magnitude, situated at the distance of three minutes 

 and a half. Who can doubt that we behold here a system 

 where each pair circulate round their centre of gravity, and 

 where the two pairs move round their own common centre of 

 gravity. Our sun is decidedly a single fixed star. If it form- 

 ed a double star with another star, this would, on account of 

 its great proximity to the sun, be distinguished by its bright- 

 ness from other fixed stars, even more so than Sirius itself, 

 and its change of position in the heavens would characterize 

 it still more surely. Let us suppose, for instance, that the time 

 of its revolution was equal to that of the companion of the 

 star p Serpen tarii, we ought to observe in the star joined 

 with our sun a proper motion of more than 7° in a year ; 

 and even if the times of its revolution were a hundred times 

 longer, its proper motion ought to be fifty times greater 

 than that of sixty-one Cygni, which is the most considerable 

 that has been observed. Another question which may be 

 started is, whether there exists between two stars of the first 

 magnitude some mutual relation similar to that of double stars, 

 and which we cannot discern on account of their great proxi- 

 mity to us. If we should find some surprising approximation 

 between the stars of the first magnitude, such a relation would 

 acquire some probability. But there is in the northern he- 

 misphere 306 stars from the first to the fourth magnitude, and 

 317 in the southern hemisphere, viz. 



1st Mag. 2d, 3d, 4th, 



In the northern hemisphere, 9 stars, 26 76 195 



southern 9 26 101 181 



The small number of stars of the third magnitude in the 

 northern hemisphere is compensated by the greater number of 

 stars of the fourth magnitude. A calculation founded upon 



