For our own purposes a fifth class can even yet be formed from the last named group—the _undoubted originals_, which will comprise only those attested by contemporary authority. The list would stand then in the order of authenticity, about as follows: I. Attested by St Augustine. _Deus Creator omnium_, _Aeterne rerum conditor_, _Jam surgit hora tertia, Qua_ Referred to directly by St. Caelestin. _Veni Redemptor gentium._ These are the _undoubted_ hymns and the only hymns to be safely assigned to Ambrose. II. _Aeterna Christi numera, et martyrum_, _Illuminans altissimus_, _Orabo mente dominum_, (from _Bis ternas horas_,) _Splendor paternae gloriae_. These are the _probable_ hymns. III. _Apostolorum passio_, _Conditor alme siderum_, _Consors paterni luminis_, _Hic est dies verus Dei_, _Jam lucis orto sidere_, _Nunc sancte nobis Spiritus_, _O lux beata Trinitas_, _Obduxere polum nubila coeli_, _O rex aeterne domine_, _Rector potens, verax Deus_, _Rerum Deus tenax vigor_, _Somno refectis artubus_, _Squalent arva soli pulvere multo_, _Summae Deus clementiae_, _Tristes erant apostoli_. These have, for one reason or another, been assigned to Ambrose. It is to be remembered that the _Tristes erant_ is a part of the _Aurora lucis rutilat_, and that in many cases the hymns are very much intermingled. A rigid designation is therefore impossible. The fourth class comprehends what may be called _Ambrosiani_—the Sedulian and Gregorian and other hymns being simply excluded from the list. IV.