80 Double Stars and the 



A reason for such a diversity in the ratios, cannot be given 

 on the hypothesis of stars optically double. This diversity 

 therefore furnishes a new proof of our preceding assertion : 

 and we may explain the reason of the small stars appearing 

 more rarely double, from the difficulty of seeing, at an im- 

 mense distance the satellite star, often much more faint than 

 the primary. 



It is remarkable that among the double stars, newly dis- 

 covered, there are several whose proper motion is already 

 known. 1 will here mention only the brilliant star y of the 

 Whale, composed of a star of the third magnitude and one 

 of the seventh ; No. 42 in Berenice's Hair, composed of two 

 stars of the sixth magnitude, remarkably near each other; 

 and y of the Crown, which, on account of the great proxim- 

 ity of the principal star of the fourth magnitude to its com- 

 panion of the seventh, is one of the most difficult to observe. 

 Our catalogue presents a considerable number of double 

 stars of this description, a part of which had probably esca- 

 ped former observers by the difficulty of distinguishing them. 

 fj of Hercules, and y of the Crown may be considered, in 

 this respect, as real touch stones of the perfection of teie- 

 scopes, and they may serve to compare the power of these 

 instruments, with that of the great telescope of Fraunhofer. 

 I have examined with this instrument, the double stars of 

 Herschell, a portion of which, such as C of Hercules, and 8 

 of the Swan had become single acc-ording to his own ob- 

 servations, and another portion were no longer double ac- 

 cording to later observers, because the power of their tele- 

 scopes was less. I have discovered that they were double 

 and have even proved the circular motion of the compan- 

 ions of the two stars above named, thus disproving the con- 

 jecture that the companion of one of them had disappeared. 

 The star •t of the Serpent, is the only one seen to be double 

 by Sir W. Herschell, which the instrument of Fraunhofer 

 shows to be single. The low altitude of the star may have 

 diminished the power of our instrument. I propose to ob- 

 serve it frequently ; for the moment will surely arrive in 

 which the companion will remove from the star whose brill- 

 iancy obscures it. The extraordinary force of our instru- 

 ment accounts also for our seeing many stars triple, which 

 were before only regarded as double. Thus Sir W. Her- 

 schell saw the star No. 7 of Taurus, as a double star of the 

 fourth class, and all subsequent observers have so regarded 



