[Illustration: Fig. 15.--Section of Cubicula with Luminare.] The Catacombs were ventilated and partially lighted by numerous openings variously called _spiragli_, or breathing-holes, and _luminari_, or light-holes. They were also probably used for the removal of the excavated material from those parts remote from the entrance. They were even more necessary for the admission of air than of light. Were it not for these the number of burning lamps, the multitude of dead bodies, no matter how carefully the _loculi_ were cemented, and the opening of _bisomi_, or double graves, for interments, would create an insupportable atmosphere. They were generally in the line of junction between two _cubicula_, a branch of the _luminare_ entering each chamber, as shown in the accompanying section of a portion of the Catacomb of Sts. Marcellinus and Peter. Sometimes, indeed, four, or even more, _cubicula_ were ventilated and partially lighted by the same shaft. De Rossi mentions one _luminare_ in the recently discovered Cemetery of St. Balbina, which is not 35 square but hexagonal, or nearly so, and which divides into eight branches, illumining as many separate chambers or galleries. Sometimes a funnel-shaped _luminare_ reaches to the lowest _piano_; but from the faint rays that feebly struggle to those gloomy depths there comes “no light, but rather darkness visible.” In the upper levels, however, some _cubicula_ are well lighted by large openings. The brilliant Italian sunshine to-day lights up the pictured figures on the wall as it must have illumined with its strong Rembrandt light the fair brow of the Christian maiden, the silvery hair of the venerable pastor, or the calm face of the holy dead waiting for interment in those early centuries so long ago. These _luminari_ are often two feet square at the top, and wider as they descend; sometimes they are cylindrical in shape, as in the Catacomb of St. Helena.[20] The external openings, 36 often concealed by grass and weeds, are very numerous throughout the Campagna near the city, and are often dangerous to the unwary rider. In almost every vineyard between the Pincian and Salarian roads they may be found, and through them an entrance into the Catacombs may frequently be effected. After the persecution had ceased, and there was no longer need for concealment, their number was increased, and they were made of a larger size, and frequently lined with masonry, or plastered and frescoed. In the Catacombs of St. Agnes and of Callixtus are several in a very good state of preservation.