| The line of the apsides of the moon's orbit revolves from west to east, through her whole course, in about nine years. |
| However, the speed of the apsides is very much slower than in the figure. |
| The line of apsides of a large proportion of comets will be approximately coincident with the solar orbit. |
| At time II the line of apsides has turned through 90 degrees and we get a symmetric eclipse, indistinguishable from a circular orbit. |
| When the line of apsides points towards the Sun, the eccentricity reaches a maximum. |
| The angle through which the radius vector rotates in going between two consecutive apsides is called the apsidal angle. |
