But better known--at least in ecclesiastical history--than even St. Brendan, is St. Cummian, surnamed "fada" or the Long, who was one of his successors in the school of Clonfert, and who perished in or a little before the great plague of 664. There are two hymns, one by himself in Latin,[12] and one in Irish by his tutor, Colman Ua Cluasaigh [Clooasy] of Cork, preserved in the "Liber Hymnorum." But his great achievement was his celebrated letter on the Paschal question addressed to his friend Segienus, the abbot of Iona. The question of when to celebrate Easter day was one which long sundered the British and Irish Churches from the rest of Europe, and has, as students of ecclesiastical history know, given rise to all sorts of conjectures as to the independence of these churches. The charge against the Irish was that they celebrated Easter on any day from the fourteenth to the twentieth day of the moon, even on the fourteenth if it should happen to be Sunday, but the fourteenth was a Jewish festival and the Council of Nice had, in 325, declared it to be unlawful to celebrate the Christian Easter on a Jewish festival.[13] The Irish had obtained their own doctrine of Easter from the East, through Gaul, which was largely open to Eastern influence; also the Irish used the old Roman cycle of 84 years, not the newer and more correct Alexandrian one of 19 years. The consequence was the scandal of having different Churches of Christendom celebrating Easter on different days, and some mourning when others were feasting, a scandal which the Epistle of Cummian was designed to put an end to. "I call this letter," says Professor G. Stokes,[14] "a marvellous composition because of the vastness of its learning; it quotes besides the Scriptures and Latin authors, Greek writers like Origen, and Cyril, Pachomius the head and reformer of Egyptian monasticism, and Damascius the last of the celebrated neo-Platonic philosophers of Athens, who lived about the year 500, and wrote all his works in Greek. Cummian discusses the calendars of the Macedonians, Hebrews, and Copts, giving us the Hebrew, Greek, and Egyptian names of months and cycles, and tells us that he had been sent as one of a deputation of learned men a few years before to ascertain the practice of the Church of Rome. When they came to Rome they lodged in one hospital with a Greek and a Hebrew, an Egyptian, and a Scythian, who told them that the whole world celebrated the Roman and not the Irish Easter."