The reference must be to the synods of Sirmium. In one held a.d. 351, against Photinus, there was a great attempt to make the semi-Arians appear orthodox, and St. Hilary accepted, while St. Athanasius rejected, their formula. Another synod was held a.d. 357, when the aged Hosius was tormented into accepting a formula, called by St. Hilary the “Sirmian blasphemy.” Another, no less injurious to the faith, was held in 358, by the desire of Constantius. During this time—but forgeries and the loss of some patristic writings make the history of the whole period somewhat uncertain—dates the weakness of Liberius, so that St. Ambrose may well speak of nutantibus sacerdotibus. See Hefele, Conc. Geschichte, I. on the Sirmian synods; Athanasius, Vol. IV. in this series, p. 464 ff.; Dict. Chr. Biog. III. 171, art. “Hosius;” Socrates, H. E., in this series, Vol. II. pp. 56, 57, 58.