Church History by Eusebius Pamphilius
Chapter XXVI.--Heraclas becomes Bishop of Alexandria.
It was in the tenth year of the above-mentioned reign that Origen removed from Alexandria to Cæsarea, leaving the charge of the catechetical school in that city to Heraclas. Not long afterward Demetrius, bishop of the church of Alexandria, died, having held the office for forty-three full years, and Heraclas succeeded him. At this time Firmilianus, bishop of Cæsarea in Cappadocia, was conspicuous.