Now such a constellation as the following must sometimes exist: the earth is in perihelion; the line of nodes coincides with the line of apsides and both lie in the line joining earth and sun.
The line of nodes rotates in a period of 18.612 years and the line of apsides in a period of 8.84 years.
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.
The line of apsides is in continual motion, generally direct, and performs a revolution in about 12 years.
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.