of the Bulherfurd Photographs. 249 



±0.6745 V-^ C — ] — 



*m + n — 2 



The weight of a right ascension or a declination at the epoch 

 1875.0 is 



49»in 

 22,ii»-f 5-3 n 



For a proper motion the weight is 



49»i/i 

 m -f- n 



Most of the stars appear on all eight plates ; for such we have 

 simply, 



Probable error of a x or of 6 X = ±0. 103 V [yv\ 



"of proper motion = zbo.028 V \yv\ 



Two of the stars were observed only on plates taken in 1877, 

 and consequently it was not possible to reduce them to the epoch 

 1875.0 by using proper motions determined from the plates them- 

 selves, as has been done for all the other stars. The proper mo- 

 tions used for these two stars are those given by Professor Schur 

 on page 298 of his memoir, and are as follows : 



Star. 



P. M. in Right Ascension. 



P. M. in Declination. 



41 



— Q^.042 



+ // .OI2 



42 



— .066 



+0 .036 



These were used for an interval of only 2.3 years. 



