318 Rutherfurd Photographic Measures. 



If we introduce into these general formulae the value of 8 for the 

 central star 24^, namely: 



5 = + 23 43' *5"-8, 

 we shall have : 



8 f — 8 = m — [4.02741] n 2 



— [8.79144] n 2 m 

 + [2.5178] 71* 



— [3-33 2 9] n2 m* 



a' — a = [0.038334] n -f [4.36678] n m 



— [8.21809] n 3 

 -J- [9.13080] ?! m 2 



— [3-459 2 ] n% m 

 + [3- 6 723] n ™ 3 



The last two terms of both expressions are insensible. 



The second table, headed Catalogue of the Pleiades, contains 

 the final places of all the stars, as derived from the photographic 

 measures alone, the following co-ordinates for 1873.0 having been 

 adopted for 24 p. 



a = 54 57' 3"-47 S = + 23 43' i5"-84 



This adopted position produces the best general agreement be- 

 tween the photographic positions of the several stars, and their 

 places interpolated to 1873.0 from the Yale and Kbnigsberg helio- 

 meter measures. It does not differ very greatly from the heliometer 

 place, which is : 



a 8 



54 57 3- 61 23 43 15.58 Elkin, 



54 57 363 23 43 15.81 Auwers, 



54 57 3-55 23 43 15.61 Newcomb, 



according to the authority we accept for the place of Alcyone. 

 Moreover, it is worthy of remark that the place of 24 p derived by 

 Elkin from his second triangulation, agrees much more closely with 

 that adopted in the present paper, than the place given above as 

 finally deduced by him from both his triangulations. The second 

 triangulation gives : 



a = 54° 57' 3"-4o fi = 2 3 ° 43' i5"-57 



Possibly the difficulty of measuring very short distances with the 

 heliometer, or the peculiar systematic errors liable to affect such 



