Latin hymnology gives a distinguished place to a hymn of twenty-three stanzas, each stanza containing four lines and beginning with a letter of the alphabet in regular order. Thus from A to Z all the letters appear except J, U, and W. Caterva is spelled Katerva, to answer for K. Y is represented by _Ymnis_, which is another form of _Hymnis_. And at last _Zelum_ concludes the list. The author struggles with a difficulty when he takes _Xeromyrrham_ to answer for X, but otherwise the ideas and versification are so excellent as to have made the hymn classic. The Roman Breviary uses two selections from it. One commences _A solis ortus cardine, ad usque_, and the other, _Hostis Herodes impie_. The general subject is the Nativity, but the poem soon proceeds to the Miracles of our Lord, and closes with an ascription of praise for His Resurrection. There can be no doubt about the authorship. Old manuscript codices, and the tradition of the Church, assign it definitely to Caelius Sedulius—sometimes called Caius Caelius Sedulius—who flourished near the middle of the fifth century. But his personal history is much harder to come at, and the few facts which we possess only stimulate our curiosity to know more. And besides, he is so entangled with another Sedulius—also a poet, also a celebrated author, also a Scot, and also involved in much obscurity—that nearly every notice of his name contains more or less of error. This second Sedulius, however, wrote no hymn which has survived, and therefore needs no further mention. He is always named Sedulius _Scotus_, to distinguish him from our Sedulius, who is invariably called _Caelius_ Sedulius. He flourished somewhere between 721 and 818, while the best ascertained date of his predecessor’s life appears to be 434. Our sources of information regarding Sedulius are Isidore of Seville and Fortunatus of Poitiers. Jerome (Hieronymus) left a catalogue of authors from the time of St. Peter to his own day. This was continued by Gennadius, as Notker of St. Gall tells us, and then it was still further extended by Isidore. Neither Jerome nor Gennadius mention our poet; the first because he died in 420, before Sedulius had achieved distinction, and the second possibly for the same reason, as his death occurred about 496 at Marseilles. Isidore (who died 636) then undertook to supply the deficiencies of the catalogue and inserted a brief note respecting Sedulius. Earlier than Isidore, however, is Fortunatus (530-609), who names our author as one of the five first Christian poets. Juvencus he dates at 330 A.D.; Sedulius flourished in the first half of the fifth century; Prudentius was converted in 405; Paulinus died in 458, and Arator was at his zenith in 560. This would seem to fix pretty closely the period to which Sedulius belongs.