76 



H. JACOBT, 





\ 



Right ascension, 291° 15' 27", 

 Polar distance 3654'.'48. 



We see, therefore, that the places in the Table require only an insign- 

 ificant correction in polar distance, and in right ascension they require the 

 correction: 



22". 



The surprisingly close agreement of the polar distance of X with 

 Auwers' place is accidental. The scale value used in the present computat- 

 ions would require a correction of — 0.002, according to a least square 

 reduction of an ordinary polar plate made at Helsingfors, in which Elkin's 

 heliometer triangulation was employed as a standard. This reduction, which 

 was made by Miss C. E. Furness of Vassar College, must have led to an 

 extremely accurate scale value for polar plates made with the Helsingfors 

 instrument. Changing the scale value by — 0.002 would change the polar 

 distance of X by — 012 only, so that we may consider our result in satis- 

 factory accord with Auwer's researches contained in Astr. Nach. 3440. The 

 plate, of course, furnishes no information as to right ascension, since the 

 zero of position angles on the plate is entirely arbitrary. None of the stars 

 measured on the plate, except X, is found in Elkin's triangulation. This is 

 due to our having selected the stars for measurement so as to satisfy as far 

 as possible the condition of symmetrical distribution about the pole. It would 

 have been better to have included more of Elkin's stars. 



It is most interesting to compare with the above the polar distance of 

 X furnished by the former solution on the supposition that the telescope did 

 not move. The values of d£ and dr\ obtained in that solution give for the 

 polar distance of X computed with equations (13), and allowing for a scale 

 value correction of — 0.002: 



Polar distance of X, 36 55?0 9. 



This differs from Auwers' value by 0?61, a quantity possibly largei 

 than can be accounted for by the uncertainty of scale value. If, therefore 

 Auwers' corrected polar distance is to be relied on, (and it differs only < 

 from the American Ephemeris), we cannot but regard the above as stro 



// 



confirmatory of our solution on the supposition that the telescope moved. 



The above discussion of measures of a trail plate is to be regarded 

 merely as a preliminary study. A more searching reduction is possible, but it 

 is best to postpone it, until a more complete set of measures can be made. 

 Enough has been done, however, to show that the method is feasible, and 

 will give very precise results. It is probable in no small degree, that these 



#W.-MaT. CTp. 76. 26 



