VESUVIUS. A volcano situated mar the eastern shore of the Bay of Naples, about 10 miles from the city of that name. It is a solitary moun tain rising from the plain of Campania, with a. base of about 30 miles in circumference, and surmounted by two summits. The higher of these is a nearly perfect cone known as Vesuvius proper. The other, of ridge-like outline, partial ly inelosing the central cone, is called Somma. Up to the year A.D. 79 Vesuvius was looked upon as a truncated mountain, its volcanic origin being unsuspected. The crater formed a deep de pression in the summit, and its sides were forest clad. Suddenly on August 24th of that year an eruption began with the appearance of a huge black cloud which rose from the mountain, accompanied by an explosion that blew off the top and rained a mass of ashes, lapilli, and mud on the towns and cities in that region. No lava was ejected in this eruption. nor in fact during any other eruption within historic times until the year 1066. In the first historic eruption Pompeii was buried under a thickness of 20 feet of loose ashes, and Herculaneum was covered by a torrent of mud. The elder Pliny, who com manded the Roman fleet at Misenum, sailed to help the distracted inhabitants. He landed near the base of the mountain and was himself suf focated by the vapors emanating from the vol cano. The younger Pliny gives a graphic account of the eruption in two letters to Tacitns (written long after the event), which are well known.
Since the year 79 there have been a number of eruptions. One occurred in the year 203, and another in the year 472. during which the ashes were carried as far as Constantinople. Other outbursts were noted in the years 512, 085, 983, and 1066. In 1031 the villages at the base
of Vesuvius were covered with lava and torrents of boiling water. During an eruption of 1779 showers of ashes, scoriae, and stones were thrown to a great height, and streams of lava poured down the side of the cone. in 1794 another vio lent outburst took place which destroyed much of the town of Tone del Greco), and in fhe eruption of 1822 the mountain is said to have lost 800 feet of its height, but most of this loss has been made imp by subsequent eruptions. Previous to this eruption of 1822 the summit is said to have been a rough and rocky plain, covered with blocks of lava and sconce, and rent by numerous fissures, from which issued clouds of smoke; it was then altered to a vast elliptical chasm, 3 miles in circumference, and about 1000 feet deep. Another remarkable eruption took place in lay, 1855, and a series of outbursts began in 1805. .lore recent eruptions have occurred in 1872, 1S78, 1880, and 1895. The present height of Vesuvius is a little over 4000 feet, and that of Sonoma 3730. The lavas of Vesuvius belong to the acid types, and among the gases hydroehrorie acid has been detected in considerable quantities. Ferric chloride often forms a yellow crust on the lava, especially in the vicinity of fumaroles. A railroad has been built from the base of the cinder cone to the summit near the edge of the crater.
Binuoonaenv. Bonney, Volcanoes (New York, 1899): Shales, Aspects of the Earth (ib., 1890) ; Lyell, Principles of (icoloyy, vol. ii. (11th ed., ib., 1889), See VOLCANO; POMPEII.