Of Ischia on the west side of the Gulf of Naples, and about 12 m.
Classical authors explained the name of Procida either as an allusion to its having been detached from Ischia, or as being that of the nurse of Aeneas.
If the islands of Ischia, at the north-west, and of Capri, at the south entrance, be included.
Still farther to the south-west lie the islands of Procida (Prochyta) and Ischia (Pithecusa, Aenaria or Inarime), which divide the Bay of Naples from the extensive Bay of Gaeta.
All this country was comprised in classical times under the title of the Phlegrean Fields, and was certainly then more actively volcanic than it now is, although the severe shock of earthquake which occurred in the island of Ischia in 1883 completely destroyed Casamicciola, and did serious damage to Forio, Lacco Ameno and Serrara Fontana, shows that there is great seismic activity in the locality.