At intervals of ten to twenty years the best-known volcano in the world–Vesuvius, on the Bay of Naples–has in the last two centuries burst into eruption, and the probability of the recurrence of this violent state of activity, at no distant date, render some account of my own acquaintance with that great and wonderful thing seasonable. We inhabitants of the West of Europe have little personal experience of earthquakes, and still less of volcanoes, for there is not in the British Islands even an "extinct" volcanic cone to remind us of the terrible forces held down beneath our feet by the crust of the earth. In regions as near as the Auvergne of Central France and the Eiffel, close to the junction of the Moselle with the Rhine, there are complete volcanic craters whose fiery origin is recognized even by the local peasantry. They are, however, regarded by these optimist folk as the products of ancient fires long since burnt out. The natives have as little apprehension of a renewed activity of their volcanoes as we have of the outburst of molten lava and devastating clouds of ashes and poisonous vapour from the top of Primrose Hill. Nevertheless, the hot springs and gas issuing from fissures in the Auvergne show that the subterranean fires are not yet closed down, and may at any day burst again into violent activity. Such also was the happy indifference with which from time immemorial the Greek colonists and other earlier and later inhabitants of the rich and beautiful shores of the Neapolitan bay before the fateful year A.D. 79, had regarded the low crater-topped mountain called Vesuvius or Vesbius, as well as the great circular forest-grown or lake-holding cups near Cumæ and the Cape Misenum, at the northern end of the bay–known to-day as the Solfatara, Astroni, Monti Grillo, Barbaro, and Cigliano–and the lakes Lucrino, Averno, and Agnano. These together with the Monte Nuovo–which suddenly rose from the sea near Baiæ in 1538 and as suddenly disappeared–constitute "the Phlegræan fields." Vesuvius was loftier than any one of the Phlegræan craters, and the gentle slope by which it rose from the sea level to a height of nearly 3700 ft. had, as now, a circumference of ten miles. It did not terminate in a "cone," as in later ages, but in a depressed, circular, forest-covered area measuring a mile across, which was the ancient crater. A drawing showing the shape of the mountain at this period is the work of the late Prof. Phillips of Oxford (Fig. 30). The soil formed around and upon the ancient lava-streams of Vesuvius appears to have been always especially fertile, so that flourishing towns and villages occupied its slopes, and the ports of Herculaneum, Pompeii, and Stabiæ were the seats of a busy and long-established population. The existence of active volcanoes at no great distance from Vesuvius was, however, well known to the ancient Greeks and Romans. The great Sicilian mountain, Etna–more than 10,000 ft. in height, rising from a base of ninety