33. The Mare Morto, the ancient Roman Harbour.
34. Baïa; behind the castle are two evident craters of ancient Volcanos.
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.
47. Island of Ischia, anciently called Ænaria, 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.
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.
To MATHEW MATY, M. D. Secretary to the Royal SOCIETY.
Since I had the pleasure of sending you my letter, in which the nature of the soil of more than twenty miles round this capital is described; examining a deep hollow way cut by the rain waters into the outside cone of the Solfaterra, I discovered, that a great part of the cone of that ancient Volcano has been calcined by the hot vapours above described. Pumice calcined seems to be the chief ingredient, of which several specimens of (as I suppose) variegated unformed marble are composed, and the beautiful variegations in them may have probably been occasioned by the mineral vapours. As these specimens are now sent to the Royal Society, you will see that these variegations are exactly of the same pattern and colours as are met in many marbles and flowered alabasters; and I cannot help thinking that they are marble or alabaster in its infant state. What a proof we have here of the great changes the earth we inhabit is subject to! What is now the Solfaterra, we have every reason to suppose to have been originally thrown up by a subterraneous explosion from the bottom of the sea. That it was long an existing Volcano, is plain, from the ancient currents of lava, that are still to be traced from its crater to the sea, from the strata of pumice and erupted matter, of which its cone, in common with those of other Volcanos, is composed, and from the testimony of many ancient authors. Its cone in many parts has been calcined, and is still calcining, by the hot vapours that are continually issuing forth through its pores; and its nature is totally changed by this chemical process of Nature. In the hollow way, where I made these remarks, you see the different strata of erupted matter, that compose the cone, in some places perfectly calcined, in others not, according as the vapours have found means to insinuate themselves more or less.