Ball — On Stars ivith a Large Annual Parallax. 22-5- 



Object. 



Date. 



Corrected 

 Distance. 



Corrected 

 Position. 



Sell], (red), 221 [a) 

 Schj. (red), 225, . 



4 22", 3660, . . 

 + 35^ 3985, . . 

 + 35", 4001, . . 



+ 35°, 4001, . . 

 rCygni, . . . 



Schj. (red), 244, . 

 + 4r, 4114, . . 



+ 4r, 4117. . . 



14 Oct., 

 17 Mav, 



1876, 

 1877, 



23 May, 1877, 



8 Oct., 1877, 



5 May, 1878, 



7 May, 1877, 



3 Sept., 1877, 



25 May, 

 6 Nov., 



1877, 

 1877, 



17 Nov., 1876, 



17 Nov., 1876, 



4 May, 1877, 



25 May, 1877, 



17 Nov., 1876, 



25 May, 1877, 



15 Nov., 1876, 



25 May, 1877, 



12 June, 1877, 



29 Nov., 1876, 



19 May, 1877, 



12 Dec, 1876, 



27 May, 1877, 



15 June, 1877, 



27 May, 1877, 



15 June, 1877, 



7 Nov., 1877, 



122" 



059 



121 



'27' 



121 



394 



121 



40 • 



48 



677 



82 



32 • 



47 



832 



82 



59 • 



48 



386 





— 



255 



704 



254 



44 • 



256 



231 



254 



40 • 



58 



693 



97 



14 • 



58 



623 



97 



29 • 



60 



430 



330 



6 • 



61 



497 



330 



5 • 



62 



019 



329 



47 • 



61 



418 



330 



1 • 



86 



466 



182 



10 ' 



86 



546 



181 



35 • 



185 



576 



78 



12 • 



185 



788 



78 



24 • 



186 



338 



78 



37 • 



124 



265 



8 



10 • 



123 



652 



7 



34 • 



211 



521 



97 



2 • 



211 



614 



97 



10 • 



211 



434 



97 



10 • 



211 



095 



67 



40 • 



210 



923 



67 



45 • 



211 



286 



67 



51 • 



20 



It then became necessary to sift these observations with the view 

 of seeing whether they afford any traces of parallax. A discrepancy 

 between the distances or positions at the dates of the two observations 

 must be attributed either, firstly, to the accidental errors of observa- 

 tion ; or, secondly, to the proper motion of one or both of the two stars ; 

 or, thirdly, to the parallax of one or both of the two stars ; or, 

 fourthly, to the joint effect of various causes. It will be convenient, 

 in considering the effect of parallax upon the position angle, to elimi- 

 nate the effect of the distance by multiplying the actual correction 

 to the position angle by the sine of the distance. If tt be the 

 parallax, and if the effect of parallax upon the distance be tt cos 6^ 

 then the effect of parallax upon the position angle will be it sin 6. 

 It follows that, when the object is observed at the apses of its paral- 



