25. The Solfaterra, anciently called Forum Vulcani: between the Solfaterra and the lake of Agnano, are the boiling waters of the Pisciarelli. 26. The New Mountain, formed by explosion in the year 1538; the sand of the sea shore at its basis burning hot. 27. The lake of Agnano, supposed the crater of an ancient Volcano: here are the baths called St. Germano, and the famous Grotto del Cane. 28. Astruni, which has been evidently a Volcano, and is now a Royal Chace, the crater being surrounded with a wall. 29. The Monte Gauro or Barbaro, anciently a Volcano. 30. The lake of Avernus, evidently the crater of an ancient Volcano. 31. Lake of Fusaro. 32. Point of Misenum, from whence Pliny the elder discovered the eruption of Vesuvius that proved fatal to him; near this place, in a vault of an ancient building, is a constant vapour, or _mofete_, of the same quality with that of the Grotto del Cane. 33. The Mare Morto, the ancient Roman Harbour. 34. Baia; behind the castle are two evident craters of ancient Volcanos. 35. Island of Procita. 36. A perfect cone and crater of a Volcano near Castiglione in the island of Ischia. 37. Lava that ran into the sea in the last eruption on this island, in the year 1301, or 1302: the place now called Le Cremate. 38. Town of Ischia and castle. 39. Lake of Licola. 40. Lake of Patria. 41. The river Volturnus. 42. Capua. 43. Caserta. 44. Aversa. 45. Mataloni. 46. Acerra. 47. Island of Ischia, anciently called AEnaria, Inarime, and Pithecusa. 48. The mountain of St. Nicola, anciently called Mons Epomeus, supposed the remains of the principal Volcano of the island. 49. Castiglione, near which are the baths of Gurgitelli. 50. Lacco, near which is that very cold vapour called by the natives _ventarole_. 51. Ancient city of Pompeii, where his Sicilian Majesty's excavations are carrying on at present. 52. Rovigliano. 53. River of Sarno. 54. Cuma. 55. Hot sands and sudatory, called Nero's baths. 56. The Lucrine lake, supposed to have been here, and of which there is still some little remain. 57. Villa Angelica, Sir William Hamilton's villa, from whence he has made many of his observations upon Mount Vesuvius. 58. Cones formed by an ancient eruption called _viuli_; here are likewise cold vapours called _ventaroli_. 59. High grounds, probably sections of cones of ancient Volcanos, being all composed of _tufa_ and strata of loose pumice and burnt matter. 60. Plain of the Campagna Felice, four or five feet of excellent soil, under which are strata of burnt and erupted matter. ...... Marks the boundary of Sir William Hamilton's observations. LETTER VI.[45] To MATHEW MATY, M. D. Secretary to the Royal SOCIETY. Naples, March 5, 1771.