By far the most definite account of the great numbers of Christians, the way in which they were looked upon by the imperial government, and the severe measures taken against them, are to be found in the notices of great pagan historians such as Tacitus and Suetonius, and more accurately and precisely in the Letter of Pliny to Trajan and in the Emperor’s reply, on which we have already dwelt with some detail. On the important and interesting question respecting the “number” of martyrs generally, one very weighty piece of evidence has been curiously neglected and ignored. This evidence comes from the Catacombs, which have been in later years the subject of so much careful and painstaking research, a research that is still proceeding. In these investigations perhaps nothing has assisted the great scholars who have devoted themselves to the work, so much as the so-called “Itineraries” or “Pilgrim Guides” to this great network of subterranean cemeteries beneath the suburbs of Rome. In the fifth, sixth, and two following centuries we know that vast numbers of Pilgrims, not only from Italy but from distant countries, visited Rome, especially with the view of reverently visiting and praying at the shrines of the brave confessors of the Faith who suffered in the days of persecution, from the time of Nero to the accession of Constantine the Great to power. To assist these pilgrim crowds, a certain number of “Itineraries” were composed. Some few of them have come down to us; these curious and interesting Pilgrim “Hand-Books” have been usually unearthed (in comparatively speaking modern times) in certain of the greater monastic libraries.[116] They date from the last years of the fifth century onwards, and were written--the copies we possess--mostly in the sixth, seventh, and eighth centuries. No doubt these “Itineraries” were copied from still older documents, and it is likely that more will be discovered. But these that we possess have been of incalculable service to the researches of men like Marchi, De Rossi, Marucchi, and their companions. The information contained in these Pilgrim Guide-Books has been found to be in most cases singularly accurate, and the details set forth have been found most strikingly to correspond with what has been discovered. Not only have the more famous shrines alluded to been identified, but even the general details have been proved to have been largely correct. One detail, however, in these ancient “Pilgrim Itineraries” has not received the attention it deserved, and which in a most striking way confirms the point urged above, that the numbers of martyrs in Rome (for we are dwelling here especially on Rome) has been greatly underrated by most historians. I