The Ecclesiastical History of Socrates Scholasticus

The Emperor Valens leaving Constantinople again set out towards Antioch; but on his arrival at Nicomedia, a city of Bithynia, his progress was arrested by the following circumstances. Eudoxius the bishop of the Arian church who has been in possession of the seat of the Constantinopolitan church for nineteen years, died soon after the emperor’s departure from that city, in the third consulate of Valentinian and Valens. The Arians therefore appointed Demophilus to succeed him; but the Homoousians considering that an opportunity was afforded them, elected a certain Evagrius, a person who maintained their own principles; and Eustathius, who had been bishop of Antioch, formally ordained him. He had been recalled from exile by Jovian, and had at this time privately come to Constantinople, for the purpose of confirming the adherents to the doctrine of the homoousion.