The Parallax of r^ Cassiox)eise. 305 



of these two ; 3'et it may not be amiss to state that if we combine, 

 to form a comparison pair, 



I with a we get ■k ^^-\- 0.282 it o. 197 weight 5. 1956 i>. e. one equation ±0.4492 

 i with h ^ = + 0.359 ± 0.124 8-0319 zho.3516 



Results by other observers for the parallax of Ti Cassiopeia are : 



O. Struve* tt = -j- 0.373 ± 0.098 by measures of jjosition angle 

 = + 0.096 zfc 0.051 " " " distance 

 concluded mean + o.''^i54 zb 0.^^045 



Schweizert and Socoloff it =.A^ 0.1386 zfc 0.0S49 by measures of position angle 



= + 0.3743 zb 0.0723 " " " distance 



concluded mean + o.^''275o zb 0.^^0551 



Struve is not explicit in his statement, but the evidence seems 

 to be that his comparison star was the same as that used by 

 ScHWEizER, namely, No. 45 on these plates, and whose position, as 

 given by the Rutherfurd measures,^ is 



a = o** 41'° 49-'555 

 0^= 57" 6' 8."87 



reduced from twelve plates whose mean epoch is 1873.016 re- 

 ferred to q Cassiopeiie at the epoch 1872.0 assuming its coordi. 

 nates at that date to be as given on page 302. This is DM. 57° 155. 

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

 equations a correction for the assumed proper motion of q Cas- 

 siopeiae may be computed from equations of the form§ 



(cos p — cos p') w -f (sin p — sin /)') v — ?/ ^=0 



where w = the correction required bj- the adopted value of p cos ^ 

 V = " " " " p sin ^ 



andp,|9' = the position angle of the comparison stars, the primed 

 letter referring alwa3'S to the less distant of the two. 



* Bulletin Physico-Mathematique de TAcademie de Saint-Petersbourg, vol. 

 xiv., p. 228, published 1855. 



fAnnales de I'Observatoire de Moscou, vol. viii., j)art 2, p. 89, published 

 1882. 



X Tlie Eutherf urd Photographic Measures of Sixty-two Stars about ;/ Cassio- 

 peiae. By Herman S. Davis. Contrib. from the Observ. of Columbia College, 

 No. 7. 



§ Annals N. Y. Acad. Sci. ; Vol. VIIL, p. 10. 



