Sixty-five Stars near 61 Cygni. 115 



The Position of 61 2 Cygni. 



26. When we correct the measured coordinates of 6i 2 Cygni 

 with respect to 61 1 Cygni, it is, of course, necessary to take into 

 account the very considerable proper motion of the measured 

 star as well as of the central star. 



On account of the shortness of time over which the Ruther- 

 eurd plates extend, a value of the relative motion deduced from 

 them alone would have very small weight. On the other hand, 

 the mean of the measured distances and of the measured angles 

 is entitled to great »weight as representing the true value of the 

 distance and angle of these stars at the mean of the dates of ob- 

 servation, 1873.546. I have, accordingly, with the latter as a 

 basis, deduced trigonometrically a set of formula? which represent 

 the motion of either of these stars relative to the other ; assuming 

 the motion of each to be uniform and on the arc of a great circle. 

 In these formulas have then been substituted constants derived 

 from the proper motion of each star separately, as determined 

 from meridian observations in the manner used in my " Declina- 

 tions and Proper Motions of Fifty-six Stars,"* to which reference 

 is made for an explanation of the method. 



27. For 61 1 Cygni I have used Auwers' values as previously 

 quoted on page 62 ; but for 61 2 Cygni the results given here have 

 been derived from the data of Table XII. 



61 1 Cygni p = 5. "20521 j = 5i°38 / 42 // £=1807. 



61 2 Cygni p = 5. 1519 2 X = 53 33 47 2 = 1858. 



By the usual formulsef these become : 



61 1 Cygni p =5. "20521 x =5i°42 / i3 // 1873.546. 



61 2 Cygni p ' = 5. 15192 x ' = 53 34 37 1873-546- 



We have also : 



Si 1 Cygni tf = 3 8°7'35" 



and from the Rutherfurd measures : 



For 61 2 Cygni, relative to 61 1 , a = 19. "3823 tt = ii4°4i'3o" at 1873.546. 



* Contribution from the Observatory of Columbia College, Neiv York. — No. 8. 

 t Chauvenet : Manual of Spherical and Practical Astronomy, Vol. I, £380. 



