544 



Froceedingti of the Iloyal Irish Academy. 



By means of these formulae I have computed the position angles 

 and distances at the different epochs of observation, and the follow- 

 ing is a comparison between the observed and computed places : — 



Epoch. 



00 



dc 



Bo-dc 



po 



P' 



po- pc 



Remarks. 



1874-66 



15-6 



14-8 



+ 0-8 



0-61 



0-53 



+ 0-08 



a i observed 

 "o-l angle. 



1874-80 



15-1 



15-6 



-0-5 



0-4 + 



0-52 



- 0-12 



a 1 computed 

 "-^^^l angle. 



1875-65 



20-1 



20-7 



-0-6 



0-54 



0-47 



+ 0-07 



_(obsen'ed 

 P° I distance. 



1876-66 



25-8 



28-5 



-2-7 



0-48 



0-40 



+ 0-08 



_ ( computt'd 

 "<= I distance. 



1877-79 



40-8 



41-9 



- 1-1 



0-32 



0-31 



+ 0-01 





1878-65 



53-7 



58-6 



- 4-9 



0-24 



0-24 



0-00 





1878-70 



59-2 



59-7 



-0-5 



obloBg. 



0-24 



— 





1880-68 



133-6 



128-4 



+ 5-2 



0-26 



0-21 



+ 0-05 





1881-50 



149-2 



150-6 



- 1-4 



0-26 



0-27 



- 0-01 





1882-60 



167-5 



170-1 



-2-6 



0-26 



0-32 



-0-06 





1883-25 



183-90 



178-5 



+ 5-4 



0-194 



0-348 



- 0-154 





1883-55 



182-50 



182-3 



+ 0-2 



0-23 



0-35 



- 0-12 





1884-71 



197-75 



195-5 



+ 2-25 



0-32 



0-36 



- 0-04 





The agreement is a tolerably close one, if we consider what a 

 close and difficult object the star is to measure. Burnham's measures 

 near the epoch 1880-68 vary from 127°-1 to 139°-5; and near 

 the epoch 1882-60, from 161°-0 to l74°-6. The measured distance, 

 0"'194, at the epoch 1883-25, is evidently too small. I find that the 

 stars were at their minimum distance, 0"-192, at the epoch 1879-91 ; 

 and in this year Burnham failed to elongate the star with the 18^- 

 inch refractor of the Dearborn Observatory, TJ. S. A. 



After completing the above calculations, I learned that the orbit 

 had been previously computed by Dnubiago. The following are his 

 elements, which are given for comparison. 



DouBiAGo's Elements of (3 Delphini. 



a = 0"-55. 

 a = 163° 34'. 

 y = 64° 54' 

 \ = 354° 36'. 

 e = 0-3567. 

 F = 26-07. 

 T = 1882-19. 



