A catacomb consists of passages or long narrow galleries cut with regularity, so that the roof and floor are at right angles to the sides, running quite straight, but crossed by others, and these again by others, forming a complete labyrinth of subterranean corridors,--the sides are honeycombed with graves. Their narrowness was to economize space, and to make the most of the limited area. These corridors, themselves the cemetery, lead into different chambers. Rome is surrounded by about sixty of these catacombs, each taking its name from the saint that reposed there. The catacombs began to be formed at the beginning of the third century A.D., and originated from a pagan tomb. We find no exception to this in the early catacombs. Just inside the gate is a pagan tomb, second century, from which a flight of steps leads into the catacomb. This tomb belonged to the family, and when it was filled, instead of building a new tomb or buying another site, they dug down and made another chamber in the tufa rock below, and so on. In the course of time the proprietor became a Christian, and probably left his property to the Church. The tomb became popular, and it was enlarged gradually; the passages serving for the poor, and the chambers for the family tombs, which were paid for. They were lighted by means of shafts, which still exist; and there was no concealment--they were the public recognized burial-places, and when Christianity was the nominal religion of the state, pagans and Christians were both buried here. We find pagan inscriptions, emblems (other than those adopted by the Christians), and pagan family tombs. The pagan frescoes are much better works of art than the Christian; for the Christians had to be educated, whilst the pagans already knew. Early Christian frescoes are very rude daubs (see those of Jonah), and they gradually advanced till the ninth century, when we have the Byzantine school (see S. Cecilia). This latter style was used for the pilgrims after the bodies, all looked upon as martyrs, were removed to the churches in Rome; which gave rise to the story that the catacombs lead to Rome, which is not true. Neither is it correct that the catacombs were old quarries used up by the Christians, though there was often an entrance into them from a quarry. Most of the inscriptions are in the Vatican and Lateran: they would be far more interesting where they were found. _N.B._--The air is pure; the vaults are dry, and they are not cold.