692 



"region, then the smaller parallactic motions in the former region 

 "will tend to diminish the precession found from the right ascensions 

 "and increase that found from the declinations", while later on p. 71 

 in drawing up his final conclusions he says: "I have already 



"remarked that a possible cause for the discrepancy ". As a 



matter of fact the galaxy, for the northern heaven is in the vernal 

 region, and for the southern in the autumnal one. 



As Nkwcomb further, according to observations of the sun and 

 of Mercury, considered as probable a correction of the assumed 

 centennial motion of the equinox in the system iV, by -j- 0".30, he 

 linally assumed <}p = -{- 0".82. With this correction, our results 

 become 



(fj, from A.R. + 0".78 

 from Decl. + .83 



dji mean -\- 0".80 



so that the discrepancy would then vanish entirely. If we do not 

 accept the latter correction, our final result is 



dp mean -j- Ö".6t}. 



There is a striking agreement between the mean of the results 

 from (t and d, as they are found by us, with that which Newcomb 

 found by eliminating the parallactic motion from the motions of the 

 individual stars, by a method corresponding in principle to one 

 given before by Kapteyn (use of the proper-motion-component t). 

 Newcomb found in this way : 



dp = -f 0".64 



or, if he accepted the corrected motion of the equinox, by estimation, 

 + 0".84. 



From this we get a strong impression that the principal un- 

 certainty- which still remains in the precessional constant according 

 to the BRAüLEY-5ter5, is i>ot due to the method of treatment, but to 

 possible errors in the catalogues compared and particularly on the 

 one hand to an error in the equinox and on the other hand to 

 periodic errors in the declinations, the Arf^. 



The precession in R.A. (the value for??;) deduced from the Groom- 

 BRiDGE-stars by Dyson and Thackeray, was already much larger 

 than the m according to Newcomb, and the discrepancy becomes 

 still greater by applying our corrections. Beside this result they deduced 

 a value for i\n from the R.A. and Decl.-observations together, which 

 is grounded upon the principle that from large and from small 

 proper motions the same R.A. of the apex must be found. It cannot 



