178 Prof. Encke o?i the Orbits of Double Stars. 



On the other hand, an excellent series of observations made 



by Bessel, by means of his great heliometer, agrees perfectly 

 with regard to the distances, and deviates in the angles of po- 

 sition. 



It is not improbable that the differences in the angles of 

 position might he removed or diminished without destroying 

 all resemblance with the present orbit. There will, however, 

 always remain a difference with regard to Herschel's obser- 

 vations, which it would be very desirable to be able to account 

 for. The great interest which the most distinguished practical 

 astronomers take in this subject leads us to expect that the 

 cause of these differences will soon be detected, and that we 

 shall then be able to decide with some certainty on the motion 

 of the double stars. 



Addition. — During the printing of these sheets, I made an 

 attempt to determine the orbit from Struve's and Bessel's ob- 

 servations, combined with those of Herschel the father. I 

 founded my calculations on these data : 



After some trials I found that for the ellipsis which would 

 represent these observations, we should have to assume : 



q^ = 3"*973, whence the following elements resulted: 



T' = 1814.'1554; tt' = 190° 37' 2"; £3 = 141° 51' 14"; 

 i' = 64° 10' 41"; <^' =■ 20^ 19' 55"; log a' = 74459; 

 fjj = 4.° 33' 6"-2 motion west. 

 The calculation of the ephemeris is contained in these 

 formulae : 



E' - (19° 54' 28") sin E' = 4° 33' 6"'2 (^-1814'1554) 



g sin 



