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day Jupiter culminates at Greenwich at 2''10 " M. T., its declination 

 being 16°48'-5 North, whereas the Sun's declination is 22°3ü' North. 

 From these data I find for the 8^'' of Julj, for Uirecht, duly making 

 allowance for refraction : 



Setting of the upper limb of the sun at 8''20'^i mean time, 

 „ Jupiter „ 9 44 -5 „ „ . 



So there is but a poor chance for an observation of the computed 

 occultation at Utrecht. For southern observatories it is somewhat 

 better. At the Cape for instance, we have : 



Sunset at 5'' 5'" mean time, 

 Setting of Jupiter ,, 7 23 ,, ,, . 



We thus find that on July 8, 1908, at Utrecht, the setting of the 

 sun precedes that of Jupiter by l''24'^-5; at the Cape by 2''20^. 



We have computed all the conjunctions of the satellites of Jupiter 

 which will occur between 31 May and 20 July 1908. In what follows 

 a short account is given of the way which led to our results. 



In the Nautical Almanac are given the Geocentric Superior Conjunc- 

 tions-, in the Almanac of 1908 they will be found on pp. 504,505. 



To begin with, a separate drawing was made of the four orbits, 

 which were supposed to be circular, for each interval of two periods 

 of I (about 85^'). On these orbits we plotted the positions of the 

 satellites for each second hour, making use of divided pasteboard arcs. 

 The number of hours elapsed since the moment chosen as a starting- 

 point were noted for each position. The equation of the centre etc. 

 was neglected. 



The scale of this drawing gave 4" to 1 mm. The radii, of the 

 orbits therefore were: for I 27 9 mm.; for II 4445 mm.; for III 

 70-9 mm. and for IV 124-7 mm. 



The direction from the Zero of I to the common centre of all 

 the circles showed the direction towards the Earth. Knowing this, we 

 could easily find for each of the six possible combinations of two of 

 the satellites, those equal hour numbers, the connecting line of which 

 is parallel to this direction. 



These connecting lines show the approximate times at which, as seen 

 from the Earth, one of the satellites is in conjunction with another. 

 The want of parallelism of the real lines joining the Earth with the 

 satellites, in different parts of their orbits, may safely be disregarded. 

 The plate annexed to this paper represents, reduced to half the scale, 

 the drawing for, the period of 85 hours, following 12 July 1908, 

 llh2m.3 M. T. Greenwich. 



The dotted lines indicate the lines connecting the equal numbers. 



