278 POOR 



The planes of the orbits of the satellites of Jupiter are all 

 nearly coincident with that of Jupiter's equator, and therefore 

 are inclined but a few degrees to the plane to which is referred 

 the comet's orbit. The elements of the orbit of the comet 

 about Jupiter show that the plane of the comet's orbit cuts that 

 in which the satellites move at a large angle, and further, the 

 difference of longitudes of the perijove and the ascending node 

 was only about 28^°. Thus, at the ascending node the comet 

 crossed the line of nodes at a large angle ; while near the de- 

 scending node the path of the comet was for a time nearly par- 

 allel to the line of nodes. Hence, as the comet neared Jupiter, 

 there could be no close approach to any of the satellites, ex- 

 cepting very near the node. But, on the other hand, as the 

 comet receded from the planet, it hovered over the satellites 

 and close approaches might occur at considerable distances 

 from the descending node. 



This is shown in Plate I, which is approximately to scale, 

 and in which the orbits of the five satellites are projected upon 

 the plane of reference, and are, therefore, seen nearly in their 

 true size. The orbit of the comet was in a plane inclined 60° 

 to this and intersecting it in the line of HU. The comet rose 

 up suddenly from below the plane of the satellites' orbits, cross- 

 ing it nearly at right angles, at H ; then passed rapidly upward 

 and almost directly over Jupiter and then slowly descended and 

 finally passed below this plane again at JJ- From the time the 

 comet passed the ascending node, at H, until it left the satellite 

 system at the descending node, was only 30 hours, of which 

 time only one half (!-<) hour was necessary to carry the comet 

 from the ascending node to perijove. 



During the time in which the comet was in the vicinity of 

 Jupiter and its satellites, it was moving so rapidly that nothing 

 except a very close approach could have any appreciable in- 

 fluence. Indeed, to have caused any noticeable alteration in 

 the relative orbit about Jupiter, the comet must have passed 

 within the "sphere of attraction " of the disturbing satelHte. 

 Now the distances of the satellites and the radii of their various 

 "spheres," taken in reference to Jupiter, are given in the table 



