galleries only 3 or 4 feet broad, with rectangular corners caused by countless intersections. Their perpendicular sides varied greatly in height and in them the burial niches, _Loculi_, were hewn out one above the other, and on the reception of the body were built up or hermetically sealed with a stone slab bearing an inscription and a Christian symbol. The wealthy laid their dead in costly marble sarcophagi or stone coffins ornamented with bas-reliefs. The walls too and the low-arched roofs were adorned with symbols and pictures of scripture scenes. From the principal passages many side paths branched off to so-called burial chambers, _Cubicula_, which were furnished with shafts opening up to the surface and affording air and light, _Luminaria_. In many of these chambers, sometimes even in the passages, instead of simple _Loculi_ we meet with the so-called _Arcosolium_ as the more usual form; one or more coffin-shaped grooves hewn out in the rocky wall are covered with an altar-shaped marble plate, and over this plate, _Mensa_, is a semicircular niche hewn out spreading over it in its whole extent. These chambers are often held in reverence as “catacomb churches,” but they are so small in size that they could only accommodate a very limited number, such as might gather perhaps at the commemoration of a martyr or the members of a single family. And even where two or three such chambers adjoin one another, connected together by doors and having a common lighting shaft, accommodating at furthest about twenty people, they could not be regarded as meeting-places for public congregations properly so called.--Where the deposit of tufa stone was sufficiently large, there were several stories (_Piani_), as many as four or five connected by stairs, laid out one above the other in galleries and chambers. According to _de Rossi’s_[103] moderate calculation there have been opened altogether up to this time so many passages in the catacombs that if they were put in a line they would form a street of 120 geographical miles. Their oldest inscriptions or epitaphs date from the first years of the second century. After the destruction of Rome by the hordes of Alaric in A.D. 410, the custom of burying in them almost entirely ceased. Thereafter they were used only as places of pilgrimage and spots where martyr’s relics were worshipped. From this time the most of the so-called _Graffiti_, _i.e._ scribblings of visitors on the walls, consisting of pious wishes and prayers, had their origin. The marauding expedition of the Longobard Aistulf into Roman territory in A.D. 756, in which even the catacombs were stripped of their treasures, led Pope Paul I. to transfer the relics of all notable martyrs to their Roman churches and cloisters. Then pilgrimages to the catacombs ceased, their entrances got blocked up, and the few which in later