78 



Double Stars and the 



my examination by zones. All the stars extending to those 

 of the eighth magnitude and even the most brilliant of the 

 ninth, which could be detected by the finder of the instru- 

 ments, were brought successively into the field of view, in 

 order to examine which among them were double. As soon 

 as a star was discovered to be double, its position was de- 

 termined by reading the index of the two circles of the in- 

 strument, as well as by the clock adjusted to sidereal-time ; 

 and a short description of the star according to its class and 

 magnitude was inscribed in the register. When the power 

 of two hundred and fourteen times, commonly employed, 

 induced a suspicion that a star was double, by exhibiting it 

 of an elongated form, a higher power extending if necessary 

 to six hundred was substituted in order to decide the case. 

 The number of stars thus passed in review may be esti- 

 mated at one hundred and twenty thousand. I then inclu- 

 ded in a catalogue the stars thus found to be double, com- 

 prehending those already known. This catalogue includes 

 three thousand and sixty three double stars of the first four 

 classes, of which three hundred and forty are found in the 

 catalogues of Herschell, and four hundred and forty in my 

 catalogue of double stars known in 1820. The following 

 table shows the increase of our knowledge relative to the 

 double stars of these four classes, and of each of them in 

 particular. 



The number of double stars is therefore nine times greater 

 in this than in Herschell's catalogue, and those of the first 

 class thirteen times greater. 



I have constructed a chart of the double stars now known, 

 situated in the northern hemisphere and to the fifth degree 

 south of the equator, which will be published as an addition 

 to the catalogue, and by which an estimate may be formed 

 of the distribution of double stars over the celestial vault. 

 This chart will show that double stars are to be found in 

 every region of the heavens ; but that their number, is less, 

 in general in those where there are the fewest stars ; and ac- 

 cordingly in the Great Bear, in a part of the Dragon, and in 



