Note 5 — Chapter I

Even so accurate and philosophical a writer as the late Professor Silliman reports on their authority that the Catacombs extend twenty miles, to the port of Ostia, in one direction, and to Albano, twelve miles, in another. Visit to Europe, vol. i, p. 329. This is impossible, as will be shown, on account of the undulation of the ground, and the limited area of the volcanic tufa in which alone they can be excavated. The number of distinct Catacombs has also been magnified to sixty; and Father Marchi estimated the aggregate length of passages to be nine hundred miles.