ove
remaining on both sides. This is close to a _luminaria_, or well for
admitting light and air, and it seems quite possible that it really
was a window, or that the upper part was made to slide down to admit
the light and air from the _luminaria_. If this was the burial-place
of Priscilla, the paintings were probably renewed in the restoration
by John I., A.D. 523. The lower part of the wall is faced with stucco
paneled with oblong panels, colored in imitation of different kinds of
marble; the stucco is about an inch thick, like slabs of marble, and
the divisions between the panels are sunk to that depth, as if each
panel had been painted before it was placed and fixed to the walls
like marble slabs. There are some long narrow slips of white stucco
lying about, which seem to have been fitted into the hollow grooves
between the slabs. The vaults in this catacomb are in many parts
supported by brick arches; in one place, at a crossing, are four small
low brick arches, the character of which agrees with the period of the
restoration in the sixth century; the mortar between the bricks or
tiles is about the same thickness as the tiles themselves, which are
rather more than an inch thick, so that there are five tiles to a
foot, including the mortar between them. These brick arches are not
subsequent repairs, but part of the original construction to carry the
vault. The _arenarium_, or sand-pit gallery, through which the present
entrance is made, has evidently been used as a subterranean road. A
branch of an aqueduct running along the side of this is part of an
extensive system of irrigation carried on throughout all this
district, the water having been brought from the Aqua Virgo, which
passed in this direction. It was probably part of the original line of
the Aqueduct, which has been altered in the portion near to Rome; this
has not been traced out to any considerable extent, but Signor de
Rossi has found many remains and indications of it. The sand-pit
roads, or _arenaria_, ran for miles parallel to the high roads, and
were probably used by the carters in preference to the open roads in
hot weather, as they are always cool.

_Christian Inscriptions_ are all funereal, and are for the most part
found in the catacombs, or subterranean cemeteries. The word cemetery
is derived from a Greek word, meaning "a sleeping place," hence the
frequent formulae in the Christian epitaphs, "dormit in pace," he
sleeps in peace; "dormitio E