10 Rutherfurd Photographic Measures. 



We therefore have the equation : 



s — s 



+ o".275 (±o".o24)-i7t, ( I - -^—~ )= + o".i5i (± 0".026) 



a solution of which gives: 



Parallax of e Cassiopeiae = -f- o".232 =b o".o67. 



This result may be regarded as confirmatory of that of Bessel, who 

 found for ^ the parallax — o". 12 =t o".29, by the method of differ- 

 ences of right ascension, using e as his comparison star. Possibly 

 a re-reduction of Bessel's observations, using the best value of the 

 proper motion, might alter his final conclusion : as it stands, it 

 seems to indicate at least an approximate equality between the 

 parallaxes of ^ and i9. 



From the values of y obtained in the solution of the normal , 

 equations I have deduced corrections for the Auwers-Bradley 

 proper motion of /t, on the assumption that the comparison stars 

 (except s) have no proper motions of their own. If we let p and x 

 have the same meaning as before, and put: 



w z= the correction required by the adopted value of p cos x 

 V = " " " " P sin X 



Then each pair of comparison stars furnishes an equation of the 

 form : 



(cos p — cos p') w "l" (sin p — sin p') v — y = o 



where p and p' are the position angles of the two stars. The equa- 

 tions so obtained are : 



Stars a and b — i Soooiv — 0.8460 u -f- 0.1534 = o 

 c and d -\- 0.0293 w — 1.9976 v — 0.1 267 = o 

 e and/ -f- 0.7563 w — 1.8116 d -f- 0.1360 = o 



from which the normal equations are : 



-(- 3.8128 w -f- 0.2112 V — 0.1770 ^= O 

 -J- 7.9S80 V — 0.6292 = O 

 and the solution is 



w = -\- 0.0421 d= o!bi47 



V = -\- 0.0777 d= 0.0102 



the probable error of one equation being zb o".o287. Applying 

 these corrections to the values previously assumed, I get: 



Corrected p sin ;j; = -}- 3" 457 Corrected p cos x ■= — ^"-53^ 



