The most important document in this department of literature, and one which bears directly upon scientific investigations, is the martyrology of Ado, Bishop of Vienne. Ado was born in northern France about 800, and entered at an early age the Monastery of Ferrières in the diocese of Sens, from whence he was sent to the Monastery of Prüm where he lived for many years under Abbot Markward (829-853). In consequence of some misunderstandings he left Prüm and went to Rome, where he spent five years and then went to Ravenna. He returned to France later and lived for some time as a simple monk in a monastery in the neighbourhood of Lyons. After the death of Bishop Agilmar of Vienne († 7th July 860) he succeeded to the see and died on the 16th December 873. He compiled the martyrology which bears his name in 858 before he became bishop,[819] the basis of his work being a very ancient martyrology with which he had become acquainted in Ravenna. If his information can be trusted, a bishop of Ravenna, whose name he does not give, received this ancient document from a bishop of Rome who is also nameless. The rest of the material he collected himself, and in particular he made notes of any information concerning martyrs which had come in his way. Many of the sources at his disposal have since been lost, thus rendering his martyrology all the more important for us. It consists of three parts: 1. A calendar containing the names of one or more saints for each day accompanied by notices naturally brief; in the printed edition it bears incorrectly the title, _Vetus Martyrologium Romanum_, given to it by its first editors, Jacob Mosander and Heribert Rosweyde;[820] 2. _A Libellus de Festivitatibus SS. Apostolorum_;[821] 3. The martyrology itself,[822] consisting of extracts from the acts of the martyrs and other writings. His preface contains matter which deserves attention.[823] He had often been urged, he says, by holy men, by his superiors, and by Bishop Remigius of Lyons to complete the martyrology; since the martyrology of Bede, which Florus had enlarged, still leaves many days without saints, he had undertaken to fill up these gaps, and for this purpose he had made use of the MSS. describing the sufferings of the martyrs, from which he had made quotations for the benefit of the weaker brethren; the ancient martyrology which came originally from Rome, served him as a foundation upon which to build. The frank avowal of his intention to fill in the spaces left vacant by his predecessors, might create a prejudice against the trustworthiness and excellence of his work, but a closer inspection will dispel this suspicion, and this would be still more the case had we the original form of the work before us; in the existing editions there are additions of a later date, such as the name Rictiovarus.