The official records of well-nigh all the Roman martyrdoms of the age of persecution, we know, were destroyed by the imperial government in the days of Diocletian. The martyrologies or histories of these heroes and heroines of the faith of Jesus which have come down to us, it is well known, were with a few notable exceptions for the most part largely composed some two or even more centuries _after_ the events they relate had happened, and have in consequence been treated by careful Christian scholars as not dependable sources of early Christian history; this has been conceded by the most scholarly of the devout Christian students. De Rossi’s great work, however, strange to say, has curiously rehabilitated very many of these long-discredited martyr stories,[121] and has clearly shown us that not a few of the more important of these have been absolutely founded on fact; of course, some of the various details as recounted in these martyrologies are more or less legendary, but the great cardinal fact of the existence, of the life-work and suffering, and noble testimony to the faith sealed with their life-blood, of these true servants of the adored Master, is positively established by what has been found in the last fifty years in the Roman city of the Christian dead. De Rossi and his companions have indeed given us a perfectly new and most striking page in the history of this early Christian Church. II It will be of special interest briefly to glance over the principal portion of the materials which De Rossi made use of as his guide during his long forty years’ labours in the exploration of the Catacombs. First in order must be taken what may be termed the literature bearing on the City of the Dead. The most important of these pieces are 1. _The Acts of the Martyrs._ These have already been alluded to as possessing, save in a few instances, little historic authority, as they were mostly composed two centuries or even more after the events which they purported to relate happened. But they were not without their value to the Catacomb explorers, for it must be remembered that when these “Acts” were put together in the form we now possess them, in the fifth, sixth, and seventh centuries, the Catacombs were still an object of eager pilgrimage from all lands, and many of the details in these “Acts” evidently were based on an historical tradition, such as the place exactly where the martyr of the “Acts” was buried; such a detail, for instance, served as a guide to the explorer. 2. _The Martyrology of S. Jerome_--a compilation dating from about the middle of the sixth century, but certainly containing memoranda of an earlier date.