According to Jerome’s Chron., Cyril became bishop in the year of Abr. 2297, or fourth year of Probus (279–280 a.d.); and Harnack accepts this as at least approximately correct. The same authority puts the accession of his successor, Tyrannus, in the eighteenth year of Diocletian (301–302 a.d.), and just below Eusebius says that the destruction of the churches (in Diocletian’s persecution) took place under Tyrannus, not under Cyril. But the Passio sanctorum quattuor coronatorum (see Mason’s Persecution of Diocletian, p. 259–271) contains a reference to him which assumes that he was condemned to the mines, and died there after three years. The condemnation, if a fact, must have taken place after the second edict of Diocletian (303 a.d.), and his death therefore in 306. There is no other authority for this report, but Harnack considers it in the highest degree probable, and the indirect way in which Cyril is mentioned certainly argues for its truth. Neither Eusebius nor Jerome, however, seems to have known anything about it, and this is very hard to explain. The matter must, in fact, be left undecided. See Harnack, Zeit des Ignatius, p. 53 sq.