His success encouraged the Academy to propose, in 1766, as a theme for competition, the hitherto unattempted theory of the Jovian system.
The long-sought cause of the "great inequality" of Jupiter and Saturn was found in the near approach to commensurability of their mean motions; it was demonstrated in two elegant theorems, independently of any except the most general considerations as to mass, that the mutual action of the planets could never largely affect the eccentricities and inclinations of their orbits; and the singular peculiarities detected by him in the Jovian system were expressed in the so-called "laws of Laplace."
Its hero is Jovian, one of the feeblest of Roman emperors, and Julian is everywhere exhibited in flaming colours as the villain of the story.
His election caused considerable surprise, and it is suggested by Ammianus Marcellinus that he was wrongly identified with another Jovian, chief notary, whose name also had been put forward, or that, during the acclamations, the soldiers mistook the name Jovianus for Julianus, and imagined that the latter had recovered from his illness.
Jovian at once continued the retreat begun by Julian, and succeeded, continually harassed by the Persians, in reaching the banks of the Tigris, where a humiliating treaty was concluded with the Persian king, Shapur II.
During his return to Constantinople Jovian was found dead in his bed at Dadastana, halfway between Ancyra and Nicaea.
Under Jovian, Christianity was established as the state religion, and the Labarum of Constantine again became the standard of the army.
Jovian entertained a great regard for Athanasius, whom he reinstated on the archiepiscopal throne, desiring him to draw up a statement of the Catholic faith.
At his hands Ephraim seems to have received baptism at the age of 18 or of 28 (the two recensions differ on this point), and remained at Nisibis till its surrender to the Persians by Jovian in 363.
Julian pressed forward to Ctesiphon but succumbed to a wound; and his successor Jovian soon found himself in such straits, that he could only extricate himself and his army by a disgraceful peace at the close of 363, which ceded the possessions on the Tigris and the great fortress of Nisibis, and pledged Rome to abandon Armenia and her Arsacid protg, Arsaces III., to the Persian.
As early as September 363, Athanasius was able to travel to Jovian, the new emperor, who had sent him a letter praising his Christian fidelity and encouraging him to resume his work.
He accompanied this emperor, for whom he expresses enthusiastic admiration, in his campaigns against the Alamanni and the Persians; after his death he took part in the retreat of Jovian as far as Antioch, where he was residing when the conspiracy of Theodorus (371) was discovered and cruelly put down.
Peter Wargentin (1717-1783), secretary to the Swedish Academy of Sciences, made a special study of the Jovian system.
Achromatic. The Jovian system has been reinforced by three remote and extremely faint members, two Perrine.
Edessa can claim no share in " the Persian Sage " Aphrahat or Afrahat (Aphraates); but Ephraem, after bewailing in Nisibis the sufferings of the great Persian war under Constantius and Julian, when Jovian in 363 ceded most of Mesopotamia to Shapur II., the persecutor of the Christians, settled in Edessa, which as the seat of his famous school (called " the Persian ") grew greatly in importance, and attracted scholars from all directions.
During the reigns of Julian and Jovian, Eunomius resided in Constantinople in close intercourse with Aetius, consolidating an heretical party and consecrating schismatical bishops.
He had been an officer of the guard under Julian and Jovian, and had risen high in the imperial service.
Then Mesopotamia enjoyed two short rests (separated by a sharp struggle) while the rivals were engaged elsewhere, when in 363 Julian made his disastrous attempt, and Jovian bought peace at the price, among other things, of Singara and Nisibis - i.e.
JOVIAN (FLAVIUS JOVIANUS) (c. 332-364), Roman emperor from June 363 to February 364, was born at Singidunum in Moesia about 332.