( 315 ) 



respectively exceed those given in the "Sterrenhemel by -|- 4" and — 8". 

 According to Leverrier we iiave, for the orbit of Jupiter in 1908,0 : 



Ascending Node = 99'31'56", 

 Inclination = i 18 29 . 



The fixed plane of tlie first satellite coincides witii the plane of 

 Jupiter's equator: the longitude of tiie ascending node on the plane 

 of Jupiter's orbit, for the beginning of 1908 is tiierefore 315°33'35", 

 the inclination 3° 4' 9". 



Furthermore ^ve have for the four fixed planes relative to the 

 plane of Jupiter's orbit : 



For the mean fixed plane of the three first satellites we thus 

 find : longitude of ascending node on the plane of Jupiter's orbit 

 at the beginning of 1908: 315°33' 35", inclination 3° 2' 6". 



Moreover we ha\'e for the respective fixed planes in 1908, according 



to TiSSERAND : 



The effect of these inclinations, however, is but trifiing. At the 

 distance of 90^ from the node they produce only deviations 



for II of l"-46, 

 ,, III „ 0"-89, 

 „ IV „ 2 01. 



The determination of tiie position of the fixed planes, as also 

 that of the planes of (lie orbits of the satellites relative to these, 

 will be much improved by the measurements which De Sitter at 

 Groningen is making on photographic plates. Eventual observations 

 of conjunctions of the satellites, rather even of occultations, will 

 contribute their part in this determination and will furnish a test 

 for the adopted values. 



21* 



