Believing, then, the catacombs to have been begun within a few years after the first preaching of Christianity in Rome, there is abundant evidence to prove that their construction was continued during the time when the Church was persecuted or simply tolerated, and that they were extended during a considerable time after Christianity became the established creed of the empire. Indeed, several catacombs now known were not begun until some time after Constantine's conversion.3 They continued to be used as burial-places certainly as late as the sixth century. This use seems to have been given up at the time of the frequent desolation of the land around the walls of Rome by the incursions of barbarians, and the custom gradually discontinued was never resumed. The catacombs then fell into neglect, were lost sight of, and their very existence was almost forgotten. But during the first five hundred years of our era they were the burial-places of a smaller or greater portion of the citizens of Rome,—and as not a single church of that time remains, they are, and contain in themselves, the most important monuments that exist of the Christian history of Rome for all that long period.
It has been much the fashion during the last two centuries, among a certain class of critics hostile to the Roman Church, and sometimes hostile to Christianity, to endeavor to throw doubts on the fact of this immense amount of underground work having been accomplished by the Christians. It has been said that the catacombs were in part the work of the heathen, and that the Christians made use of excavations which they found ready to their hand. Such and other similar assertions have been put forward with great confidence; but there is one overwhelming and complete answer to all such doubts,—a visit to the catacombs themselves. No skepticism can stand against such arguments as are presented there. Every pathway is distinctly the work of Christian hands; the whole subterranean city is filled with a host of the Christian dead. But there are other convincing proofs of the character of their makers. These are of a curiously simple description, and are due chiefly to the investigations of late years. Nine tenths of the catacombs now known are cut through one of the volcanic rocks which abound in the neighborhood of Rome. Of the three chief varieties of volcanic rock that exist there, this is the only one which is of little use for purposes of art or trade. It could not have been quarried for profit. It would not have been quarried, therefore, by the Romans, except for the purposes of burial,—and the only inscriptions and other indications of the character of the occupants of these burial-places prove that they were Christian.4 They are very different from the sepulchres of the great and rich families of Rome, who lined the Appian, the Nomentan, and Flaminian Ways with their tombs, even now magnificent in ruin; very different, too, from the columbaria, or pigeon-holes, in which the ashes of the less wealthy were packed away; and still more different from the sad undistinguished ditch that received the bodies of the poor:—
"Hoc miserae plebi stabat commune sepulcrum."
It not unfrequently happens in the soil of the Campagna, that the vein of harder rock in which the catacombs are quarried assumes the soft and sandy character which belongs to it in a state of decomposition. The ancient Romans dug this sand as the modern Romans do; and it seems probable, from the fact that some of the catacombs open out into arenaria, or sandpits, as in the case of the famous one of St. Agnes, that the Christians, in time of persecution, when obliged to bury with secresy, may have chosen a locality near some disused sandpit, or near a sandpit belonging to one of their own number, for the easier concealment of their work, and for the safer removal of the quarried tufa. In such cases the tufa may have been broken down into the condition of sand for removal. In later times, as the catacombs were extended, the tufa dug out from one passage was carried into the old passages no longer used; and thus, as the catacomb extended in one direction, it was closed up in another, and the ancient graves were concealed. This is now one of the great impediments in the way of modern exploration; and the same process is being repeated at present; for the Church allows none of the earth or stone to be removed that has been hallowed as the resting-place of the martyrs, and thus, as one passage is now opened, another has to be closed. The archaeologists may rebel, but the priests have their way. The ancient filling up was, however, productive of one good result; it preserved some of the graves from the rifling to which most were exposed during the period of the desertion of the catacombs. Most of the graves which are now found with their tiled or marble front complete, and with the inscription of name or date upon them unbroken, are those which were thus secluded.
But there is still another curious fact bearing upon the Christian origin of the catacombs. They are in general situated on somewhat elevated land, and always on land protected from the overflow of the river, and from the drainage of the hills. The early traditions of the Church preserve the names of many Christians who gave land for the purpose,—a portion of their vignas, or their villas. The names of the women Priscilla, Cyriaca, and Lucina are honored with such remembrance, and are attached to three of the catacombs. Sometimes a piece of land was thus occupied which was surrounded by property belonging to those who were not Christian. This seems to have been the case, for instance, in regard to the cemetery of St. Callixtus; for (and this is one of the recent discoveries of the Cavaliere de Rossi) the paths of this cemetery, crossing and recrossing in three, four, and five stages, are all limited to a definite and confined area,—and this area is not determined by the quality of the ground, but apparently by the limits of the field overhead. There can be no other probable explanation of this but that Christians would not extend their burial-place under land that was not in their possession. Many other facts, as we shall see in other connections, go to establish beyond the slightest doubt the Christian origin and occupation of the catacombs.
Descending from the level of the ground by a flight of steps into one of the narrow underground passages, one sees on either side, by the light of the taper with which he is provided, range upon range of tombs cut, as has been described, in the walls that border the pathway. Usually the arrangement is careful, but with an indiscriminate mingling of larger and smaller graves, as if they had been made one after another for young and old, according as they might be brought for burial. Now and then a system of regularity is introduced, as if the fossor, or digger, who was a recognized officer of the early Church, had had the leisure for preparing graves before they were needed. Here, there is a range of little graves for the youngest children, so that all infants should be laid together, then a range for older children, and then one for the grown up. Sometimes, instead of a grave suitable for a single body, the excavation is made deep enough into the rock to admit of two, three, or four bodies being placed side by side,—family graves. And sometimes, instead of the simple loculus, or coffin-like excavation, there is an arch cut out of the tufa, and sunk back over the whole depth of the grave, the outer side of which is not cut away, so that, instead of being closed in front by a perpendicular slab of marble or by tiles, it is covered on the top by a horizontal slab. Such a grave is called an arcosolium, and its somewhat elaborate construction leads to the conclusion that it was rarely used in the earliest period of the catacombs5. The arcosolia are usually wide enough for more than one body; and it would seem, from inscriptions that have been found