However this may be, there have existed since the eighth century numerous MSS. of a collection of the names of the martyrs of all times and countries belonging to the Roman Empire which went by the name of the _Martyrologium Hieronymianum_, and to which was attached two reputed letters of St Jerome to Chromatius, Bishop of Aquileia, and to Heliodorus, Bishop of Altinum. The work corresponds to that mentioned by Cassiodorus. Upon close examination, it is quite clear that the work, as we have it now, cannot have been composed by St Jerome. It includes the names of many persons who lived at a date subsequent to St Jerome, as, for example, to name one out of many, St Gregory the Great on the 12th March. In other respect the names do not extend beyond the seventh century, as appears upon an inspection of the earliest codices. In later recensions we naturally meet with the names of many persons who lived at a still later date. As regards the date of composition, the personality of the compiler and kindred questions, we are face to face with an historical and literary problem resembling that of the Pseudo-Isidorian Decretals and the Donation of Constantine. Still some light has now been cast upon these difficulties, since we have at last a thoroughly critical text of the document, the investigations of De Rossi and Duchesne having determined which of the existing MSS. is the earliest.[773] Among the MSS. belonging to the eighth century, is one written for the Monastery of Weissenburg in the diocese of Spires, now preserved in Wolfenbüttel, _Codex Wisseniburgensis_, 23. De Rossi believed it was written shortly before the death of Abbot Wando († 756) of Fontanelle in the diocese of Rouen, because his death has been added by a later hand on _XV. Kal. Mai_. It is certain that the codex was written before 772, because this date is referred to in it. Of about the same period is the Parisian Codex 10 837, belonging to Echternach. It is written in an Anglo-Saxon hand, and is perhaps somewhat later than the former, but is derived from an original MS. certainly older than the Weissenburg Codex. This view which is that of De Rossi gains support from the fact that the two festivals in honour of the Holy Cross are not contained in the codex, while they appear in the Weissenburg and all later codices. Both codices are full of errors of grammar and spelling. The codex from the monastery of Hilariacum originally belonging to Metz and now at Berne, is more correct and better written, but unfortunately only extends to the 21st November. The latest entries made in it by the first hand belong to the year 766 and refer to Bishop Chrodegang. The text dates from the time of Clotaire II. (584-628).