Astronomy. — ''Investigation concerning the precession-constant and 

 ike systematic proper-motions of the stars". By Dr. C. de 

 Jong. (Communicated by Prof. E. F. van de Sande Bakhuyzen). 



(Communicated in the meeting of September 2H, 1917). 



In a former paper in tliese Proceedings, 1 have given a resumé 

 of the results of a determination of the precession-constant and 

 tlie systematic proper-motions of the stars, obtained by the 

 comparison of Küstneh's catalogue of 10663 stars (Veröff. der Königl. 

 Sternwarte Bonn, N°. 10) with some zone-catalogues of the "Astro- 

 nomische Gesellscliaft." Since then I have continued tlie investigation 

 with new material, comnjencing with the jiroper-motions deduced 

 from a comparison oï Küstner's catalogue with Besset/s zone-obser- 

 vations between 0° and -|- 1^° declination. Although I have published 

 the resuhs of this investigation together with those previously 

 obtained in my dissertation ^), and hope in a fui-ther extended and 

 completed investigation (which will include all Bessel's zone-obser- 

 vations in so far as they occur in Küstner) to publish all these 

 results at its full length, I beg to offer here a short resume of the 

 recently completed second part and of the conclusions which would 

 appear to follow from the investigations so far accompli-shed. Together 

 with this I shall give a comparison of my results with these of 

 similar investigations by others, the lattei' being reduced afresh by 

 the means at present at our disposal. 



1. Immediate comparison. 



Bessel's coordinates (in future referred to as B. Z.) were taken 

 from the original publication of the zones by Bessei. in the "Astro- 

 nomische Beobachtungen auf der Königl. Univ. Sternwarte zu 

 Koningsberg", Abth. VII— XVII, 1821—1833. These coordinates are 

 reduced to 1825 by Luther's reduction tables (Astr. Beob. Königs- 

 berg. Abth. XXXVII, Th. II) and then, after having been freed as 

 far as possible of errors by the corrections in Abth. XXXVII, Th. I 

 and from Ristenpart's Fehlerverzeichniss, compared with the coor- 

 dinates reduced to 1825 in Küstner's C!atologue (Kü). It then appeared 

 that, with the exception of 29 double stars, which were excluded, 



') Onderzoekingen omtrent de praecessiekonstaute en de stelselmatige Eigen- 

 bewegingen der sterren, Leiden 1917. 



