In the service of the Roman Church used at the removal of the bodies of the holy martyrs from their graves in the catacombs is a prayer in which are the words,--"Thou hast set the bodies of thy soldiers as guards around the walls of this thy beloved Jerusalem";--and as one passes from catacomb to catacomb, it is, indeed, as if he passed from station to station of the encircling camp of the great army of the martyrs. Leaving the burial-place of St. Agnes, we continue along the Nomentan Way to the seventh milestone from Rome. Here the Campagna stretches on either side in broad, unsheltered sweeps. Now and then a rough wall crosses the fields, marking the boundaries of one of the great farms into which the land is divided. On the left stands a low farm-house, with its outlying buildings, and at a distance on each side the eye falls on low square brick towers of the Middle Ages, and on the ruinous heaps of more ancient tombs. The Sabine mountains push their feet far down upon the plain, covered with a gray-green garment of olive-woods. Few scenes in the Campagna are more striking, from the mingling of barrenness and beauty, from the absence of imposing monumental ruins and the presence of old associations. The turf of the wide fields was cropped in the winter by the herds driven down at that season from the recesses of the Neapolitan mountains, and the irregular surface of the soil afforded no special indications of treasures buried beneath it. But the Campagna is full of hidden graves and secreted buildings.