190 G. H. KNIBBS. 



stated, Bessel had found from 71 stars that the poles of proper 

 motion were so distributed over the spherical surface that the 

 determination of a parallactic equator seemed hopeless. From 

 the proper motions of 3,268 stars of the Auwers-Bradley catalogue 

 1,374 poles whose uncertainty of position did not exceed 10 ,o 5 

 were accepted and divided into six classes. The distribution of 

 these on the celestial spherical surface was analysed by dividing 

 it into trapeziums and triangles at every 10° by hour and declina- 

 tions circles, and observing the distribution thereon. Kobold 

 concluded that by this analysis, it is certainly demonstrated that 

 the Besselian method conducts to an apex, for the solar motion, 

 not sensibly different from 



R.A.=266-°1, D.= + 0-°4 

 as deduced in his earlier essay from 622 stars, He discussed the 

 reason why different methods should lead to results so much at 

 variance ; for example, Argelander's method leads to the result 



R.A.=260-°8, D. = '+31-°3 

 but Bessel's to 



R.A.=261-°4, D.= -6-°0, 



the cause of difference he concluded is not to be sought in the 

 difference of data but in the treatment thereof. The essential 

 feature of Argelander's method is that it supposes the stellar 

 proper motions to be analogous to errors of observation. An 

 examination shews most obviously, that the "law of error" is not 

 applicable, and therefore its application can lead only to false 

 results. Kobold pointed out that the magnitude of the sun's 

 motion is comparable to that of the stars, and discussed the cases 

 where it is supposed very great, or on the other hand negligible 

 in relation thereto. He stated that Airy made the same assump- 

 tion as Argelander, modified only by the addition that the distance 

 of the stars is reciprocally proportional to their proper motion. 

 Airy's solution really depended for the element of distance on 

 magnitude. 1 The fuller discussion of the result by Argelander's 

 method and by Bessel's seemed to prove that the latter is 

 altogether preferable. 



1 Monthly Not. Roy. Astr. Soc, Vol. xix., p. 178. 



