they have the compass of high treble, are usually alto. When the boy arrives at the age of puberty, the alto changes into tenor or bass.-Voice is also the name given to a part assigned to a human voice or an instrument in a composition.

VOIGTLAND (in law Latin, Terra Advocatorum); in a wider sense, all that part of Germany which formerly belonged to the imperial bailiffs (in German, Voigte, Latin, advocati), the ancestors of the present princes and counts of Reuss. It comprised the Saxon circle of Voigtland, the bailiwic of Weida and Ziegenrück, in the grand duchy of Saxe-Weimar, the territories of the princes and counts of Reuss, the district of Hof, now included in the Bavarian circle of the Upper Maine, and the Saxe-Altenburg bailiwic of Ronneburg. From the eleventh century there were imperial officers, in the above described region, who bore the name of bailiffs (advocati, voigte) of the holy Roman empire, and who managed the affairs of the emperor. In a narrower sense, the term is applied particularly to a circle of Saxony, consisting of a part of the former Voigtland. It has 102,891 inhabitants on 680 square miles, and is also called the circle of Neustadt. The chief town is Plauen. It contains some mountainous and woody districts, and in some parts is well adapted for pasturage and tillage. The most remarkable peculiarity is the pearl-fishery in the river Elster (see Pearl), which is sometimes very productive, and has yielded some pearls of much beauty.

VOITURE, Vincent, a celebrated French wit, was born at Amiens, in 1598. His agreeable manners and conversation introduced him to good company; and he was a visitor at the Hôtel de Rambouillet, and was also well received at court, and by Gaston, duke of Orleans, who made him his master of the ceremonies. In 1634, he was admitted into the French academy, and was subsequently sent on a mission to Spain, where he composed some verses in such pure and natural Spanish, that every body ascribed them to Lope de Vega. He also visited Rome and England, and died in 1648. Voiture was one of the first persons in France distinguished by the title of bel esprit. He wrote verses in French, Spanish and Italian. The former are occasionally easy and sprightly, but have much strained wit and affected sentiment. His letters place him high in the class of epistolary writers, though they often degenerate into affec

tation, insipid pleasantries, and far-fetched allusions.

VOLATILE OILS. (See Essential Oils.) VOLATILITY, in chemistry; the quality of a substance, to evaporate in a certain degree of heat: it is the opposite to fixidity. It is very probable, that all substances are capable of being volatilized, and that we should be able to dissolve every one of them by fire, but for the want of a sufficient degree of heat.

VOLCANOES. The volcano and the earthquake might, perhaps, with no impropriety, have been treated of together, since both are undoubtedly effects of the same subterranean process; but we have preferred to devote to each a separate article, as the phenomena on the earth's surface, to which they give rise, are considerably different. The present article will, however, embrace several particulars relating to earthquakes, which were omitted in the article under that title, on account of their close connexion with the subject of volcanoes. There are certain regions to which volcanic eruptions, and the movements of great earthquakes, are confined: over the whole of vast tracts active volcanic vents are distributed at intervals, and most commonly arranged in a linear direction. Throughout the intermediate spaces there is abundant evidence that the subterranean fire is continually at work; for the ground is convulsed, from time to time, by earthquakes: gaseous vapors, especially carbonic acid gas, are disengaged plentifully from the soil; springs often issue at a very high temperature, and their waters are very commonly impregnated with the same mineral matters which are discharged by volcanoes during eruptions. Of these great regions, that of the Andes is one of the best defined. Commencing southward, at least in Chile, at the forty-sixth degree of south latitude, it proceeds northward to the twenty-seventh degree, forming an uninterrupted line of volcanoes. The Chilean volcanoes rise up through granitic mountains. Villarica, one of the principal, continues burning without intermission, and is so high, that it may be distinguished at the distance of 150 miles. A year never passes in this province without some slight shocks of earthquakes; and about once in a century, or oftener, tremendous convulsions occur, by which the land has been shaken from one extremity to the other, and continuous tracts, together with the bed of the Pacific, have been raised permanently from one to twenty feet above their former level.

ing Caribbean sea must be considered as a theatre of earthquakes and volcanoes. On the north lies the island of Jamaica, which, with a tract of the contiguous sea, has often experienced tremendous shocks; and these are frequent along a line extending from Jamaica to St. Domingo and Porto Rico. On the south of the same basin, the shores and mountains of Colombia are perpetually convulsed. On the west is the volcanic chain of Guatimala and Mexico, and on the east, the West Indian isles, where, in St. Vincent's and Guadaloupe, are active vents. Thus it will be seen that volcanoes and earthquakes occur, uninterruptedly, from Chile to the north of Mexico; and it seems probable, that they will hereafter be found to extend, at least, from cape Horn to California. In regard to the eastern limits of the region, they lie deep beneath the waves of the Pacific, and must therefore continue unknown to us. On the west, they do not appear, except where they include the West Indian islands, to be prolonged to a great distance; for there seem to be no indications of volcanic disturbances in Guiana, Brazil and Buenos Ayres. On an equal, if not a still grander scale, is another continuous line of volcanic action, which commences on the north, with the Aleutian isles in Russian America, and extends first in an easterly direction for nearly two hundred miles, and southward, without interruption, throughout a space of between sixty and seventy degrees of latitude, to the Moluccas, and then branches off in different directions both towards the east and north-west. The northern extremity of this volcanic region is the peninsula of Alaska, in about the fifty-fifth degree of latitude. Thence the line is continued, through the Aleutian or Fox islands, to Kamtschatka, in the southern extremity of which there are seven active volcanoes, which, in some eruptions, have scattered ashes to immense distances. The Kurile chain of isles constitutes the prolongation of the range in a southern direction; the line is then continued to the south-west in the great island of Jesso, where there are active vents. Between the Japanese and Philippine islands, the communication is preserved by several small insular vents. The line is then prolonged through Sanguir, and the north-eastern extremity of Celebes, to the Moluccas. Here a great transverse line may be said to run from east to west. On the west, it passes through the whole of Java, where there are thirty-eight large

Hot springs are numerous in this district, and mineral waters of various kinds. Pursuing our course northward, we find in Peru only one active volcano as yet known; but the province is so subject to earthquakes, that scarcely a week passes without a shock; and many of these have been so violent as to create great changes of the surface. Farther north, we find, in the middle of Quito, where the Andes attain their greatest elevation, Tunguragua, Cotopaxi, Antisana and Pichincha, the three former of which not unfrequently emit flames. From the first of these, a deluge of mud descended in 1797, and filled valleys, 1000 feet wide, to the depth of 600 feet, forming barriers, whereby rivers were dammed up, and lakes occasioned. Earthquakes have, in the same province, caused great revolutions in the physical features of the surface. There are three volcanoes farther north, in the province of Pasto, and three others in that of Popayan. In the provinces of Guatimala and Nicaragua, which lie between the isthmus of Panama and Mexico, there are no less than twenty-one active volcanoes. This great volcanic chain, after having pursued its course for several thousand miles from south to north, turns off in a side direction in Mexico, and is prolonged in a great plateau, between the eighteenth and twenty-second degrees of north latitude. The plateau in question owes its present form to the circumstance of an ancient system of valleys, in a chain of primary mountains, having been filled up, to the depth of many thousand feet, with various volcanic products. Five active volcanoes traverse Mexico from west to east; viz. Tuxtla, Orizaba, Popocatepetl, Jorullo and Colimia. Jorullo, which is in the centre of the great plateau, is no less than forty leagues from the ocean, which shows that the proximity of the sea is not a necessary condition, although certainly a very general characteristic, of the position of active volcanoes. The extraordinary eruption of this mountain in 1759 will be described in the sequel. To the north of Mexico there are three, or, according to some, five volcanoes, in the peninsula of California. In the year 1812, violent earthquakes convulsed the valley of the Mississippi at New Madrid, for the space of three hundred miles in length. As this happened exactly at the same time as the great earthquake of Caraccas, it is probable that these two points are parts of one continuous volcanic region; for the whole circumference of the interven

volcanic mountains. In the volcanoes of Sumatra, the same linear arrangement is preserved. In another direction, the volcanic range is prolonged through Borneo, Celebes, Banda, New Guinea; and farther eastward in New Britain, New Ireland, and various parts of the Polynesian archipelago. The Pacific ocean, indeed, seems, in equatorial latitudes, to be one vast theatre of igneous action; and its innumerable archipelagoes, such as the New Hebrides, Friendly islands, and Georgian islands, are all composed either of coralline limestones or volcanic rocks, with active vents here and there interspersed. In the old world, the volcanic region extends from east to west for the distance of about 1000 miles, from the Caspian sea to the Azores, including within its limits the greater part of the Mediterranean and its most prominent peninsulas. From south to north, it reaches from about the thirty-fifth to the fortyfifth degree of_latitude. Its northern boundaries are Caucasus, the Black sea, the mountains of Thrace, Transylvania and Hungary, the Austrian, Tyrolian and Swiss Alps,-the Cevennes and Pyrenees, with the mountains which branch off from the Pyrenees westward, to the north side of the Tagus. Its western limits are the ocean; but it is impossible to determine how far it may be prolonged in that direction; neither can we assign with precision its extreme eastern limit, since the country beyond the Caspian and sea of Aral is scarcely known. The southern boundaries of the region include the most northern parts of Africa, and part of the desert of Arabia. We may trace, through the whole of the area comprehended within these extensive limits, numerous points of volcanic eruptions, hot springs, gaseous emanations, and other signs of igneous agency; while few tracts of any extent have been entirely exempt from earthquakes throughout the last 3000 years. Besides the continuous spaces of subterranean disturbance, of which the outline has been given above, there are other disconnected volcanic groups, of which the geographical extent is, as yet, imperfectly known. Among these may be mentioned Iceland, which belongs, perhaps, to the same region as the volcano in Jan Mayen's island. With these, also, part of the nearest coast of Greenland, which is sometimes shaken by earthquakes, may be connected. The island of Bourbon belongs to another theatre of volcanic action, of which Madagascar probably forms a part, if the al

leged existence of burning volcanoes in that island shall be substantiated. Respecting the volcanic system of Southern Europe, it may be observed, that there is a central tract, where the greatest earthquakes prevail, in which rocks are shattered and cities laid in ruins. On each side of this line of greatest commotion, there are parallel bands of country where the shocks are less violent. At a still greater distance, as in Northern Italy, there are spaces where the shocks are much rarer and more feeble. Beyond these limits, again, all countries are liable to slight tremors at distant intervals of time, when some great crisis of subterranean movement agitates an adjoining volcanic region; but these may be considered as mere vibrations, propagated mechanically through the external crust of the globe, as sounds travel almost to indefinite distances through the air. Shocks of this kind have been felt in England, Scotland, Northern France and Germany, particularly during the Lisbon earthquake.

We shall now give some account of a few of the principal volcanic vents, dispersed through the great regions before described, and consider the composition and arrangement of their lavas and ejected matter. From the first colonization of Southern Italy by the Greeks, Vesuvius afforded no other indication of its volcanic character than such as the naturalist might infer from the analogy of its structure to other volcanoes. These were recognised by Strabo. The ancient cone was of a very regular form, terminating, not, as at present, in two peaks, but with a flattish summit, where the remains of an ancient crater, nearly filled up, had left a slight depression, covered in its interior by wild vines, and with a sterile plain at the bottom. On the exterior, the sides of the mountains were covered with fertile fields, richly cultivated, and at its base were the populous cities of Herculaneum and Pompeii. But the scene of repose was at length doomed to cease, and the volcanic fire was recalled to the main channel, which, at some former, unknown period, had given passage to repeated streams of melted lava, sand and scoriæ. The first symptom of the revival of the energies of this volcano was the occurrence of an earthquake, A. D. 63, which did considerable injury to the cities in its vicinity. From that time to the year 79, slight shocks were frequent; and in the month of August of that year, they became more numerous and violent, till

they ended at length in an eruption. The elder Pliny, who commanded the Roman fleet, was then stationed at Misenum; and, in his anxiety to obtain a near view of the phenomena, he lost his life, being suffocated with sulphureous vapors. His nephew, the younger Pliny, remained at Misenum, and has given us, in his Letters, a lively description of the awful scene. A dense column of vapor was first seen rising vertically from Vesuvius, and then spreading itself out laterally, so that its upper portion resembled the head, and its lower, the trunk of the pine, which characterizes the Italian landscape. This black cloud was pierced, occasionally, by flashes of fire as vivid as lightning, succeeded by darkness more profound than night. Ashes fell even upon the ships at Misenum, and caused a shoal in one part of the sea. The ground rocked, and the sea receded from the shores, so that many marine animals were seen on the dry sand. The appearances above described agree perfectly with those witnessed in more recent eruptions, especially those of Monte Nuovo, in 1538, and of Vesuvius, in 1822. In all times and countries, indeed, there is a striking uniformity in the volcanic phenomena; but it is most singular that Pliny, although giving a circumstantial detail of so many physical facts, and enlarging upon the manner of his uncle's death, and the ashes which fell when he was at Stabiæ, makes no allusion whatever to the sudden overwhelming of two large and populous cities, Herculaneum and Pompeii. (q. v.) Tacitus, the friend and contemporary of Pliny, when adverting, in general terms, to the convulsion, says merely, that "cities were swallowed up or buried" (haustæ aut obrute urbes. Hist. lib. i.). It does not appear that, in the year 79, any lava flowed from Vesuvius: the ejected substances appear to have consisted entirely of sand and fragments of older lava. In 1036, the first eruption of flowing lava occurred. A second happened in 1049, and a third in 1138; after which a great pause ensued of 168 years. During part of 1301, earthquakes had succeeded one another with fearful rapidity; and they terminated at last with the discharge of a lava stream from a point named the Campo del Arso, not far from the town of Ischia. This lava ran quite down to the sea-a distance of about two miles. Its surface is of a reddish-black color; and it is almost as sterile, after a period of five centuries, as if it had cooled down yester

day. The next eruption occurred in 1306; between which era and 1631, there was only one other (in 1500), and that a slight one. During this interval, a memorable event occurred in the Phlegræan fields-the sudden formation of a new mountain in 1538. Frequent earthquakes for two years preceding disturbed the neighborhood of Pozzuoli; but it was not until the twenty-seventh and twentyeighth of September, 153, that they became alarming, when not less than twenty shocks were experienced in twenty-four hours. At length, on the night of the twenty-ninth, two hours after sunset, a gulf opened between the little town of Tripergola, which once existed on the site of the Monte Nuovo, and the baths in its suburbs, which were much frequented. A large fissure approached the town with a tremendous noise, and began to discharge pumice-stones, blocks of unmelted lava, and ashes mixed with water, and, occasionally, flames. The ashes fell in immense quantities, even at Naples. The sea retired suddenly for two hundred yards, and a portion of its bed was left dry; and the whole coast from Monte Nuovo to beyond Pozzuoli was upraised to the height of many feet above the bed of the Mediterranean, and has ever since remained permanently elevated. On the third of October, the eruption ceased, so that the hill Monte Nuovo, which is 440 feet above the level of the bay, and a mile and a half in circumference at its base, and which was chiefly thrown up in a day and a night, was accessible. The depth of its crater is 421 feet from the summit of the hill, so that its bottom is only nineteen feet above the level of the sea. For nearly a century after the birth of Monte Nuovo, Vesuvius still continued in a state of tranquillity. Bracini, who visited Vesuvius not long before the eruption of 1631, gives the following description of its interior. The crater was five miles in circumference, and about one thousand paces deep. Its sides were covered with brush wood, and at the bottom there was a plain on which cattle grazed. In the woody parts, wild boars frequently harbored. But at length these forests and grassy plains were suddenly consumed-blown into the air, and their ashes scattered to the winds. In December, 1631, seven streams of lava poured at once from the crater, and overflowed several villages on the sides and at the foot of the mountain. Great floods of mud were as destructive as the lava itself; for such (as often happens during

these catastrophes) was the violence of the rains produced by the evolution of aqueous vapor, that torrents of water descended the cone, and, becoming charged with impalpable volcanic dust, rolled along loose ashes, acquiring such consistency as to deserve the appellation of aqueous lava. A brief period of repose ensued, which lasted only until the year 1666, from which time to the present, there has been a constant series of eruptions, with rarely an interval of rest exceeding ten years. The modern lavas of Vesuvius are characterized by a large proportion of augite. When they are composed of this mineral and feldspar, they differ in composition but slightly from many of the trap-rocks. (See Trap.) They are often porphyritic, containing disseminated crystals of augite, leucite, or some other mineral, imbedded in a more earthy base. These porphyritic lavas are often extremely compact. In the lava currents of central France (those of Viverais), the uppermost portion, often forty feet or more in thickness, is an amorphous mass passing downwards into lava, irregularly prismatic; and under this there is a foundation of regular and vertical columns, in that part of the current which must have cooled most slowly. A great variety of minerals are found in the lavas of Vesuvius and Somma. Augite, leucite, feldspar, mica, olivine, specular iron, idocrase, garnet and sulphur are most abundant. It is an extraordinary fact, that, in an area of three square miles round Vesuvius, a greater number of mineral species have been found than in any spot, of the same dimensions, on the surface of the globe. Many of these are peculiar to this locality. A small part of the ejected matter, however, remains so near to the volcanic orifice. A large portion of sand and scoriæ is borne by the winds and scattered over the surrounding plains, or falls into the sea; and much more is swept down by torrents into the deep during the intervals, often protracted for many centuries, between eruptions. These horizontal deposits of tufaceous matter become intermixed with sediment of other kinds, and with shells and corals, and, when afterwards raised, form rocks of a mixed character, such as tufas, peperinos and volcanic conglomerates. Besides the ejections which fall on the cone, and that much greater mass which finds its way gradually to the neighboring sea, there is a third portion, often of no inconsiderable thickness, composed of alluvions, spread over the valleys and plains, at small distances from the volcano. Im

mense volumes of aqueous vapor are evolved from a crater during eruptions, and often for a long time subsequently to the discharge of scoriæ and lava. These vapors are condensed in the cold atmosphere surrounding the high volcanic peak; and heavy rains are caused sometimes even in countries where, under other circumstances, such a phenomenon is entirely unknown. The floods thus occasioned sweep along impalpable dust and light scoriæ, till a current of mud is produced, which is often more dreaded than an igneous stream, from the greater velocity with which it moves. After Vesuvius, the most authentic records relate to Etna, which rises, near the sea, in solitary grandeur, to the height of nearly 15,000 feet, the mass consisting chiefly of volcanic matter ejected above the surface of the water. The base of the cone is eighty-seven miles. Etna appears to have been in activity from the earliest times of tradition. Thucydides informs us that between the colonization of Sicily by the Greeks and the commencement of the Peloponnesian war (B. C. 431), three eruptions had occurred. A great eruption occurred in the year 1669. The lava, after having overflowed fourteen towns and villages, some having a population of between 3000 and 4000 inhabitants, arrived, at length, at the walls of Catania. These had been purposely raised to protect the city; but the burning flood accumulated till it rose to the top of the rampart, which was sixty feet in height, and then fell in a fiery cascade, and overwhelmed part of the city. The wall, however, was not thrown down, but was discovered long afterwards by excavations made in the rock by the prince of Biscari; so that the traveller may now see the solid lava curling over the top of the rampart, as if still in the very act of falling. This great current had performed a course of fifteen miles, before it entered the sea, where it was still 600 yards broad and 40 feet deep. A gentleman of Catania, named Pappalardo, desiring to secure the city from the approach of the threatening torrent, went out with a party of fifty men, whom he had dressed in skins to protect them from the heat, and armed with iron crows and hooks. They broke open one of the solid walls which flanked the current near Belpasso, and immediately forth issued a rivulet of melted matter, which took the direction of Paternò; but the inhabitants of that town, being alarmed for their safety, took up arms, and put a stop to further operations. In 1811, the great crater testified, by its violent detonations,