It has been urged in objection to this theory, that the difficulty of secretly disposing of at least a hundred millions of cubic feet of refuse material taken from the Catacombs must have been exceedingly great, unless it could be removed under cover of employment for some economic purpose. It will be shown, however, that secrecy was not always necessary, as has been assumed, but that, on the contrary, the Christian right of sepulture was for a long time legally recognized by the Pagan Emperors; and that the Catacombs continued to be publicly used for a considerable time after the establishment of Christianity on the throne of the Cæsars. During the exacerbations of persecution there is evidence that the excavated material was deposited in the galeries already filled with graves, or, as we have seen, in the spacious vaults of adjacent _arenaria_. If the Catacombs were merely excavations for sand or stone, as has been asserted, we ought to find many of their narrow galleries destitute of tombs, and many of the _arenaria_ containing them; whereas every yard of the former is occupied with graves, and not a single grave is found in the latter, nor do they contain a single example of a mural painting or inscription. The conclusion is irresistible that the Catacombs proper were created exclusively for the purpose of Christian burial, and in 44 no case were of Pagan construction. The erroneous theory here combated has arisen, as we have said, chiefly from certain classical allusions to the _arenaria_, and from passages in the ancient ecclesiastical records describing the burial places of the martyrs, as _in cryptis arenariis_, _in arenario_, or _ad arenas_. Some of these localities, however, have been identified beyond question, and found to consist merely of a sandy kind of rock, and not at all of the true _pozzolana_. In others a vein of _pozzolana_ does actually occur in the Catacombs, or they are connected with ancient _arenaria_, as at St. Agnes and at Calixtus. In the other instances the localities are either yet unrecognized, or the expression merely implies that the cemetery was _near_ the sand pits--_juxta arenarium_, or _in loco qui dicitur ad Arenas_. The mere technical description of the Catacombs, however, gives no idea of the thrilling interest felt in traversing their long-drawn corridors and vaulted halls. As the pilgrim to this shrine of the primitive faith visits these chambers of silence and gloom, accompanied by a serge-clad, sandaled monk,[22] he seems like the Tuscan poet wandering through the realms of darkness with his shadowy guide. “Ora sen’ va per un segreto calle Tra l’ muro della terra.”[23]