S6 Professor Struve on Double and Triple Stars, as 



some, such as £ Herculis and 3 Cygni, had become single, ac- 

 cording to his own observations, and of which others had no 

 longer been found double by subsequent observers, because 

 their instruments had not sufficient power. I have recognized 

 that they were double, and I even saw the circular motion of 

 the companions of the two stars mentioned above, which dis- 

 proves what has been conjectured, that the companion of one 

 of these stars had disappeared. The star r Serpentarii is the 

 only one seen double by Sir W. Herschel, which the great 

 telescope of Fraunhofer has shown single. The small altitude 

 of the star might have weakened the power of our telescope. 

 I intend, however, to observe it often : for the time will cer- 

 tainly come when the companion will separate itself from the 

 star, whose brightness hinders us from seeing it. It is owing 

 also to the extraordinary power of our telescope that we are 

 able to see many triple stars, which were before only known as 

 double ones. Thus Sir W. Herschel has seen the star No 7, 

 Tauri, as a double star of the fourth class, and all subsequent 

 observers have also seen it thus, the principal star being of 

 the sixth magnitude, and its companion of about the tenth. 

 But our telescope has shown that the principal star is itself a 

 double star of the first class, composed of two similar stars of 

 the seventh magnitude. According to the observation of Sir 

 William Herschel, also those made at Dorpat, and those of Mr 

 Herschel Junior and Mr South, the star -fy Cassiopeia? was 

 considered as double. But our telescope has shown that the 

 companion itself is composed of two stars nearly united of the 

 ninth magnitude. All astronomers provided with good in- 

 struments have observed a trapezium of four stars of various 

 brightness, which are found in the middle of the nebulae of 

 Orion. The two Herschels, and Schroeter in particular, have 

 examined this curious object. However, our telescope has en- 

 abled us to see a fifth star, which has not been remarked by 

 any of the preceding observers, although, since I have com- 

 municated this discovery to Mr Herschel Junior, he has also 

 distinguished it with a reflecting telescope of 20 feet. Is this 

 little star of the number of the changeable stars, or does it 

 still exist ? These conjectures appear to me to be entitled to 

 more consideration, as I had never seen this star in my first 



