"Well, yes," said the Trappist in reply to the ladies' questions, "the corridor is scarcely more than a yard in width; two persons could not pass along side by side. How they dug it? Oh! it was simple enough. A family or a burial association needed a place of sepulchre. Well, a first gallery was excavated with pickaxes in soil of this description--granular tufa, as it is called--a reddish substance, as you can see, both soft and yet resistant, easy to work and at the same time waterproof. In a word, just the substance that was needed, and one, too, that has preserved the remains of the buried in a wonderful way." He paused and brought the flamelet of his candle near to the compartments excavated on either hand of the passage. "Look," he continued, "these are the /loculi/. Well, a subterranean gallery was dug, and on both sides these compartments were hollowed out, one above the other. The bodies of the dead were laid in them, for the most part simply wrapped in shrouds. Then the aperture was closed with tiles or marble slabs, carefully cemented. So, as you can see, everything explains itself. If other families joined the first one, or the burial association became more numerous, fresh galleries were added to those already filled. Passages were excavated on either hand, in every sense; and, indeed, a second and lower storey, at times even a third, was dug out. And here, you see, we are in a gallery which is certainly thirteen feet high. Now, you may wonder how they raised the bodies to place them in the compartments of the top tier. Well, they did not raise them to any such height; in all their work they kept on going lower and lower, removing more and more of the soil as the compartments became filled. And in this wise, in these catacombs of St. Calixtus, in less than four centuries, the Christians excavated more than ten miles of galleries, in which more than a million of their dead must have been laid to rest. Now, there are dozens of catacombs; the environs of Rome are honeycombed with them. Think of that, and perhaps you will be able to form some idea of the vast number of people who were buried in this manner."