Зображення сторінки
PDF
ePub

CHAP. XVII.

VESUVIUS.

POMPEII. — NEA

NOTES ON NAPLES -SCENERY.
POLITAN PEOPLE.-CAUSES OF THEIR LOW CONDITION.

This

THE Bay of Naples will not disappoint the expectation of the most imaginative of the tribe of wanderers. Distant mountain peaks tipped with snow rising in the clear intensely blue sky, are encircled by the deep green forests, below which bright pasture and grass fields join to a rich network over the face of the country of vineyards, orchards, olive and orange groves, hamlets, towns, villas, terraces, white walls, and a dazzling confusion of the works of nature and of man. splendid hill-skirting terminates in sea-cliffs, some black, some yellow, some bare, some bending over the waves under the tangled luxuriance of southern vegetation. High over all, the graceful outline of Vesuvius loses itself in the column of smoke which rises, and spreads in the heavens, concentrating the innumerable details of the vast scene into one harmonious glorious whole. But this magnificence of nature must be seen: it cannot be described. It is seen to most advantage from the sea. On shore you want a suitable foreground. You are shut in between white walls on a dusty road, or stand upon terraces with vineyards and orchards, row behind row, all around you; and although these may please at a great distance, they have but a patchy, dotty effect near the eye, as the foreground of scenery. The poet-painter would scarcely select such objects for the foreground of his landscape. They are too artificial. The great clearness of the Italian atmosphere, the absence of mist, vapour, or exhalation partially hiding, partially showing distant objects, and thus giving the mind play upon them, is also against the picturesque

effect of this scenery in general. All is distinctly seen. There is no delusion, or rather there is the delusion that distances appear smaller, and elevations lower than they actually are. In our northern scenery, from the vapour in the atmosphere, the refraction of the rays from a distant mountain makes it visually, and to the sense of sight positively, higher than the actual measurement confirms: and where mist and cloud partially hide the mountain, there is a mental refraction magnifying the unseen, as well as a visual refraction enlarging the seen. It is this difference of the medium through which a country is viewed, and which in our cloudy atmosphere brings our own imaginations to act on objects of mountain scenery, that makes the traveller from the north doubt whether the mountains he sees so clearly and minutely in the south are really so much higher than those he has been accustomed to see half hid in mist and vapour.

Vesuvius is an isolated mountain about three miles from the sea, of an elevation of 3,792 feet. An American would call it an elegant mountain, and no English. word can better express its character, so graceful are the flowing outlines of its slopes from the base to the summit, on every side. Vesuvius has been prodigiously higher than it now is, for the Monte Somma, a peak about 800 yards north of the present cone, and Ottaiana on the south, are apparently peaks remaining of the circumference of the base of some vast ancient cone. These three remaining peaks, of which Monte Somma is the highest, belong to one mountain-base, although divided above by chasms of the vast extinct crater, and, by ravines below, and the whole mountain-mass is a single independent elevation on a vast plain, and unconnected with the Apennines. To ascend Vesuvius is no very difficult feat. The stranger is beset with guides waiting at Portici with their mules and asses, and, like watermen at the Tower stairs, clamorous for a fare, and so violent in their gesticulations, that the traveller

cano, and were quarrelling about their shares of the meat. But it is the custom of these people to scream at the top of their voices in ordinary conversation, and to use their hands and arms, as well as their tongues, as explanatory organs. In fact no guide is necessary, there being a regular foot-path, and the shape of the ground, to lead any one accustomed to hills, and the foot-path is well frequented at all hours. You ride up to the hermitage, a house of two stories high like an old Highland manse, about half way up, or about an hour and a quarter's walk from the beginning of the ascent. It is situated on the dividing ridge between the ravine through which the lava of the ancient crater of Monte Somma has flowed, and that through which the lava of the present crater, in its recent eruptions, has partly taken its course. It is a ridge formed apparently by the deposition of stones and ashes from the volcano, upon a natural feature of the ground rock of the mountain. The hermitage is at the end of the cultivated ground on the side of Vesuvius. Above it, all is lava or scoriæ, and some of this rubbish was still so hot that lava ejected eight months before ignited dry leaves thrust into its crevices. At this hermitage you may get hermit's fare for your money, a bottle of good wine and an omelette and ladies are carried to the summit from hence in about an hour and a half, in a sort of sedan-chair, with about as much fatigue and danger, as in being sedanned on a frosty night from the lowest to the highest of the fashionable streets of the city of Bath.

Is there any reason for supposing that the fire-seat, the focus of this volcano, is situated far below the level of the plain on which the mountain stands, and is not contained altogether, or principally, within the walls of the mountain itself? Travellers and geologists are very apt to run poetical, when they fall in with burning mountains. They tell us that this and the other great volcanoes of the world are vents of a great central fire in the interior of our globe. How does this vast central

fire burn without known communications with atmospheric air or water? At what depth below the crust of the earth is it in activity? In the last eruption of Vesuvius in 1839, the elevation in the air to which luminous matter, stones or ashes were thrown, was estimated or guessed by intelligent observers to be about one half of the apparent height of the mountain. In the great eruption of the 8th of August, 1779, the height of the column of flame, or ignited matter, was estimated at one and a half the height of the mountain, or 1800 yards and Sir William Hamilton even reckons it to have been 3,600 yards, or above two miles high. Stones, as large as hogsheads, are stated by the Abbé de la Torre to have been projected to the elevation of 400 yards. In 1775, a mass of lava of 120 cubic feet is stated by De Bottis to have been projected to an elevation from which he reckoned the descent to have occupied nine seconds of time. This fact would also give an elevation of about 400 yards. Now the projecting force cannot have been working at any immense distance below, such as the semidiameter of the earth, nor at any considerable portion of it, because gravity and atmospheric resistance would oppose the elevation of huge masses of stone through such a space. No solid masses of matter, such as stones, rocks, lava, could be projected entire and compact, against the column of air through such a distance; but would come to the surface of the earth from such a depth, be the crust over this central focus ever so thin, in a liquid or gaseous state. The points of ejection, also, the vents of a central fire-action, would naturally be always and invariably in the points of least resistance; that is, in the lowest plains, not in the points of greatest resistance, the summits of high and weighty mountains resting on the plains. The prodigious power of volcanic agency on and above the surface of the earth, is the strongest proof that the focus of that power is at no immense distance below its visible energy. The supposed communications between

faterra, are not supported by historical facts of any correspondence between their eruptions. The communication even of this volcanic focus with the sea, at three miles' distance, is very doubtful, and rests only upon the ejection of torrents of water in one or two of the recorded eruptions: but besides the explanation of rainwater accumulating in the hollow of the crater, and at one period forming in it a small pond or lake, the gases evolved in the combustion within the crater might, by their combination in the air, produce water. Water from the sea passing through such a focus of fire, would undoubtedly be ejected in a gaseous state.

The most instructive appearance to the traveller who carries the ordinary smattering of geological theory with him is, that the ashes, cinders, dust, stones, whether loose, or indurated and cemented by pressure, heat, or other causes, into tufa rock more or less compact in short, all ejected matter from the volcano that is not ejected in a liquid state like lava, is deposited in a distinct order or stratification. The larger particles are in one regular bed, above which is another bed of finer, above that another and another of finer and finer particles, each bed lying with a certain character of regularity above the other, as in water depositions; and then comes another bed or layer of rougher, larger particles, and a similar gradation of finer regularly above it. Where the tufa rock is laid bare in section, as by the road leading to the hermitage, and also in the rocks about Naples, and in the excavations at Pompeii, this stratified tendency of the ejected matter is to be seen. When the matter-dust, ashes, fine particles, stonesis ejected, the densest falls first to the ground, is the first deposited from the atmosphere, exactly as if water instead of air had been the medium in which the particles had been suspended. Then follow bed after bed,

*

*Goethe in his observations, dated 6th March, 1787, on Vesuvius in a state of eruption, says, that the heavy pieces of rock fell first and rolled down the cone with a deadening noise; the smallı

« НазадПродовжити »