had sheltered them from the violence
of persecutors were abandoned, and replaced by those of local martyrs.
Thus the catacomb of Domitilla became that of Nereus and Achilleus;
that of Balbina was named for S. Mark; that of Callixtus for SS.
Sixtus and Caecilia; and that of Maximus for S. Felicitas.

One characteristic of Christian epigraphy shows what a comparatively
safe place the catacombs were. Inscriptions belonging to them never
contain those requests to the passer to respect the tomb, which are so
frequent in sepulchral inscriptions from tombs above-ground, and which
sometimes, on Christian as well as pagan graves, take the form of an
imprecation. An epitaph discovered by Hamilton near Eumenia, Phrygia,
contains this rather violent formula: "May the passer who damages my
tomb bury all his children at the same time." In another, found near
the church of S. Valeria, in Milan, the imprecation runs: "May the
wrath of God and of his Christ fall on the one who dares to disturb
the peace of our sleep."

The safety of the catacombs was not due to the fact that their
existence was known only to the proselytes of Christ. The magistrates
possessed a thorough knowledge of their location, number, and extent;
and we have evidence of raids and descents by the police on
extraordinary occasions, as, for instance, during the persecutions of
Valerian and Diocletian. The ordinary entrances to the catacombs,
which were known to the police, were sometimes walled up or otherwise
concealed, and new secret outlets opened through abandoned pozzolana
quarries (_arenariae_). Some of these outlets have been discovered, or
are to be seen, in the cemeteries of Agnes, Thrason, Callixtus, and
Castulus. In May, 1867, while excavating on the southern boundary line
of the Cemetery of Callixtus, de Rossi found himself suddenly
confronted with sandpits, the galleries of which came in contact with
those of the cemetery several times. The passage from one to the other
had been most ingeniously disguised by the _fossores_, as those who
dug the catacombs were called.[149]

The defence of these cemeteries in troubled times must have caused
great anxiety to the Church. Tertullian tells how the population of
Carthage, excited against the Christians, sought to obtain from
Hilarianus, governor of Africa, the destruction of their graves. "Let
them have no burial-ground!" (_areae eorum non sint_) was the rallying
cry of the mob.

The catacombs are unfit fo