When, therefore, we proceeded in a second paper to question the same subterranean sanctuaries on another subject of Christian doctrine—the supremacy of St. Peter—we called into court another set of witnesses altogether: to wit, the paintings of their tombs and chapels. Exception has been taken against the competency of these witnesses, on the plea that they are not old enough; they were not contemporary, it is said, with those first ages of the church whose faith is called in question. To this we answer that the objection is entirely out of date; it might have been raised twenty or thirty years ago, and it might have been difficult at that time satisfactorily to dispose of it. Those were days in which writers like M. Perrot in France could affect to pronounce dogmatically on the age of this or that painting, solely on the evidence of its style, without having first established any standard by which that style could be securely judged. There are still a few writers of the same school even at the present day, such as Mr. Parker in England, who assigns precise years as the dates of these subterranean monuments with as much confidence as if he had been personally present when they were executed, and (we may add) with as wide a departure from the truth as if he had never seen the pictures at all. Such writers, however, have but few disciples nowadays. Their foolish presumption is only laughed at; and it is not thought worth while seriously to refute their assertions. Men of intelligence and critical habits of thought are slow to accept the _ipse dixit_ of a professor, however eminent, upon any subject; and all who have studied this particular subject—the paintings in the Catacombs—are well aware that the question of their antiquity has now been carried beyond the range of mere conjecture and assumption; it has been placed on a solid basis of fact through the indefatigable labors of De Rossi. Those labors have been directed in a very special way towards establishing the true chronology of the several parts of the Catacombs; and when this had been done, it was manifest to all that the most ancient _areæ_ were also those which were most abundantly decorated with painting, whilst the areæ that had been used more recently—_i.e._, in the latter half of the fourth or beginning of the fifth century—were hardly decorated at all. This gradual decline of the use of pictorial decoration has been traced with the utmost exactness through the successive _areæ_ of a single Catacomb; six or seven tombs being found thus decorated in the first _area_, two in the second, one in the third, none at all in the fourth; and the same thing has been seen, with more or less distinctness, throughout the whole range of subterranean Rome. Then, again, every casual visitor to them can see for himself that before the abandonment of burial here—_i.e._, before the year 410—many of the paintings were already considered old enough to be sacrificed