Astronomy. "On the pertnrhations 171 the motion of Hyperion 

 proportional to the first poicer of Titaifs eccentricity ' . By 

 Dr. .1. WoLTJEK Jr. (Cotiinimiieated bv Piof. W. dk Sitter). 



(Communicated in tlie meeting of March 29, 1919). 



1 . The object of this paper consists of the computation of those terms in 

 the motion of Hyperion that are proportional (o the first power of Titan's 

 eccentricity, under the restrictions mentioned in Chapter II § 1 of tiie "In- 

 vestigations" '). The arguments of these perturbations are fornied by 

 combining tlie secular pait of the ditference in longitude of pericentre 

 for the satellites with multiples of the argument of the libration. 

 If this multiple is an odd mnnber, the coelKicienls in the mean 

 anomaly contain the square root of the disturbing mass as divisor; 

 the value of the corresponding perluil)ation of the mean anomaly 

 (and mean longitude) can amount to about half a degree. It is 

 obvious to sup[)0se that here we are concerned with those pertur- 

 bations, which H. Stki:vi-;*) mentioned at the conclusion of his 

 discussion of the orbit of Hyperion; their influence clearly was 

 stated by him from observation; according to his estimation their 

 value also could amount to about half a degree. 



This paper forms a continuation of the "Investigations" and 

 of "The longitude of Hyperion's pericentre and the mass of Titan" ^). 



2. The terms of the four variables Q,(},^,Si, of the first order 

 with respect to Titan's eccentricity, viz. (i(j,')ö,(f^,(fl> are determined 

 l)y the following system of linear differential equations *) : 



1) .Investigations in the theory of Hyperion. Here after to be cited as "Inves- 

 tigations." 



») Publications de I'Observatoire Central Nicolas. Série II. Vol. XI. Beobach- 

 tungen der Saturnstrabanten. St. Pétersbourg. 1898. p. 290. 



») Proceedings, Vol. XXI, N». 6 and 7. 



*) Investigations, p. 48. 



