A line joining the moon in perigee and in apogee is called the " line of apsides."
On comparing observations made at different times it was found that the line of apsides was not fixed, but made a complete revolution in the heavens, in the order of the signs of the zodiac, in about nine years.
The "line of apsides" is that which joins them, forming the major axis of the orbit.
The line of apsides is in continual motion, generally direct, and performs a revolution in about 12 years.
They are called the lower or nearer, and the higher or more distant apsides respectively.
This line was called the line of apsides.
Tisserand in 1895.1 It involved the action of no third mass, but depended solely upon the progression of the line of apsides in a moderately elliptical orbit due to the spheroidal shape of the globes traversing it.