The Parallax of yj Cassiopeise. 303 



The resulting values for the separate stars and plates are given 

 in Table III., pages 308-9. From them we derive as the par- 

 allax coefficient for any one of the equations of Table Y. 



where /S'g and ^'4 refer alwa^'s to the less distant comparison 

 star of the pair. 



It seemed to me desirable, in view of the exceedingly great 

 difficulty of getting comparison stars suitably situated either with 

 respect to position angle or distance, to take a larger number 

 than usual, and I have consequently- reduced six pairs, being all 

 that were impressed on the plates sufficiently often in both sea- 

 sons of the .year, and the present paper includes all six, though 

 onh' tliree of them are so situated with reference to the parallac- 

 tic ellipse as to give good coefficients for -. Every observation 

 and ever}' plate was used. 



In Table II., page 308, will be found the approximate positions 

 of these stars relative to the central star which the accompanying 

 diagram also represents graphically-, and shows in addition the 

 direction of the axes of the parallactic ellipse and of the proper 

 motion of 7^ Cassiopeije. 



It should be stated, however, that the circle does not repre- 

 sent the limits of the field of view, nor are the distances given on 

 the same scale as those of the plates at the focus of the telescope; 

 the diagram is intended to give only roughly the relative location 

 of the stars used in this investigation. It will be noticed how the 

 N. E. quadrant is inconveniently void of stars bright enough to 

 be impressed on the plates at all seasons of the 3-ear. 



The star designated as No. 16 was so numbered by Rutherfurd 

 on the plates when measured, but is the same star as No. 45, in 

 order of right ascension, referred to on page 305. 



