( 424 ) 



du 

 We can derive the values of ^ directly from the comparison of 



the two former computations with A M= -{- 40" and A il/ =: -]- 50". 

 And so I find for the three dates of the observations: 



AM— — O.bOe Arc 



— 0.549 Ajt 



— 0.573 A;r 



If we keep Jt constant and want to substitute apart of the correc- 

 tion of M by a variation of <fi, we must satisfy the relation 



Aï; = 

 or 



\0(p Jv const. 



fdM\ 

 I derived the values of T — bv computing from the three values 



VO^/y const. 



of V, with a varied excentricity, the corresponding values of the 

 mean anomaly. Hence I got for the three observations: 



AM = — 1.040 A(p 



— 1.186 A^ 



— 1.260 Ar/) 



Although the coefficients as well those of Ajt as of Ag) show a 

 small variation in the influence of the corrections of the elements 

 on the three positions, practically this influence differs too little from 

 that of a constant variation of M to allow a determination of 

 A3J, A(f) and Ajt separately from the three observations. 



Leiden, November 1906, 



Mathematics. "On the locus of the imirs of common points and 

 the envelope of the common chords of the curves of three 

 pencils" (1^* part). By Dr. F. Schuh. (Communicated by 

 Prof. P. H. Schoute). 



1. Given three pencils (6V), (Cs), (C«) oj- plane curves of degree 

 r, s, t. To find the locus L of the pairs of points throitgh ivhich 

 passes a curve of each of those pencils. 



Let P and P' be the points of such a pair. When determining 

 the locus we shall notice but those points P and P' which are for 

 each couple of pencils movable points of intersection (i. e. points not 

 necessarily coinciding with the basepoints), a distinction to be made 

 only when the pencils have common basepoints. The locus L arrived 



