Note 111 — Chapter IV · PART I. THE AQUEDUCTS. (continued 2)

There is Opus Reticulatum of rude and early character (more like the Opus Incertum of the Emporium than the mausoleum of Augustus) at the entrance of this passage, which is mentioned by Nibby. There is a stone-quarry also at the entrance, of the hard, dark-coloured stone used for making roads, and excellent for that purpose. This is the same stone that is called selce or silex in Rome, and seems to be similar to the hard lava under which Herculaneum is buried, and of which there are quarries near the tomb of Cecilia Metella.