« ElőzőTovább »
lava, the infamed air, reduced to the size of the crater, at length escapes, spinning round and round. Breaking the top of the shaft, it bears it along in a thousand pieces, with soot, ashes, and pumice, with which the sides of the abyss within were loaded. In this hor. rible whirlwind it is even common to see huge pieces of calcined rock, torn from the bosom of the mountain, carried into the air.
• The display of this phænomenon, in its extent and duration, depends upon the degree of force in the circumstances we have just mentioned. When the parts first raised lose this force, and, being left to their own weight, would naturally sink, those that come next, being still themselves supported, repel and throw them off. At that juncture an overspreading of the fire takes place at the top of the column, which adds to its beauty. I think it must have been from this view of it that the younger Pliny drew his comparison be. tween the production of that eruption of Vesuvius, by which his uncle was killed, and of which he was himself an eye-witness, and the cypress tree,
• In a short time the whole of the column turns into a horrible shower of red hot rocks, Aints, and ashes. Monstrous burning masses are seen bounding, and rolling down the side of the mountain. Woe be to those places which lie in the direction of the wind prevailing at the time of this tremendous shower! Pompeii, HerculaDeum, and Stabiæ, three towns to the south-west of Vesuvius, disappeared about seventeen centuries ago by a similar occurrence : and it was only in this century (the eighteenth) that they were discovered. A column, such as that we have been describing, broke over them, and the land about them : they were buried more than hifty feet under a mass of ashes and calcined Aints, which was farther covered by a bed of lava several feet deep. If the wind be violent the ashes are carried to an incredible distance.' P. 125. · The ashes and other substances ejected by volcanic fires are various.' The former were not however the cause of the dry fog in 1783, which seems to have been a phænomenon connected with electricity, though in what way is yet unknown. The other matters thrown out by volcanoes are sufficiently known; but the author has not detailed them scientifically. The flow of the lava is poetically described ; yet the reader will observe that this wall of solid fire does not inflame a stick stuck into it, nor scorch the hand which holds the frying-pan- an experiment often tried over it. . . In this view it is a real river of fire at its source. The red hot lava issues in immense bubbles. It does not however become a rapid current even on the declivity of the mountain, but rolls heavily, being of a consistency, as we have already observed, very compact and adhesive. As it descends, the stream widens: it burns up every thing consumable by fire in its way. Its waves seem to be inexhaustible; they reach the plain in millions upon millions, often presenting to view a breadth of a mile and a half, and oft-times more. Here the following waves with difficulty press and impel those before : they rise one above the other in piles. At a certain distance from
the crater, when the air has made a sensible impression on the lava, it fows in a body from twelve to fifteen feet high, over which the stream is constantly collecting anew. It is a wall of solid fire ; for to windward one may approach near enough to touch the matter with a pole, and try its resistance ; although to leeward it is not to be borne within thirty paces without danger of suffocation. One might suppose that the top of these accumulated and moving bodies would concrete and become fixed, but it is not so: the dreadful heat they contain keeps them in a state sufficiently liquid to occasion the gradual rolling off of the mass; for it is in that manner that a stream of lava continues to run, and form a prolongation of this amazing wall. Five weeks after the eruption of 1794 the centre of the thickest part of the lava was red-hot. The progression of the matter, thus continues as long as it is supplied from the crater, which does not cease disgorging until, after an emission more or less copious, the effervescence in the remainder of the matter contained in the gulf begins to subside. Then it still appears for some time bubbling at the rim of the crater, and afterwards contracts and sinks insensibly, till at last the mountain is restored to its usual calm.' P. 139.
The quantity of lava disgorged is immense ; but the author does not recollect that it is very often porous, and that its specific gravity is inconsiderable. Among the matters ejected is sometimes water, when apparently this fluid is in greater proportion than the heat can convert into steam. It is an idle question to contest whether it proceed from the sea or reservoirs of fresh water. Each may occasionally supply the shower; and it is equally futile to dispute whether the matter discharged come from the middle or below the base of the mountain; for the question can never be decided.
The causes of the extinction of volcanoes are examined; but on these we need not enlarge, as many of them are imaginary. The extinction of the volcanoes in the Grecian islands in the Archipelago is attributed to the Euxine bursting through the Bosporus of Thrace -- a circumstance that cannot admit of proof, and on which the negative would be as probable as the affirmative. Some observations on the Giant's Causeway are subjoined ; and the author discusses the question of these columns being volcanic somewhat superficially:-he leaves it undecided.
Several of the following chapters contain a catalogue of the different volcanoes hitherto known in different countries. It is, so far as our recollection reaches, complete; and, in some disputed mountains, the author's decisions seem to be judicious, Of these there are ninety-nine on the continents, and ninety in the islands. Seventy-eight of the former are in America. Of the continental volcanoes, a large proportion is near the sea. The connexion we can only explain from this circumstance that subterraneous fires are not uncommon, but that a coincidence of water is necessary to produce the explosion. Let it
however be recollected, that of the interior of Africa, and many parts of South America, we know little. Were these regions better explored, the disproportion might not be so great.
Of the mud volcanoes the account is curious. We shall select the description of one in the island of Taman, in the mouth of the river Cuban, in the Taurida. Another is in Sicily; and, during an eruption which ensued from it, the local temperature of the earth was lower than that of the surrounding air.
This last eruption took place in February 1794. It was the greatest and most copious ever known. It happened at the top of a hill situated at the north point of Taman, near the bay of the same name. The appearance of the place seems to indicate that there had been a similar eruption at a period far back. The ground not covered over by the last is of the same nature as the more recent sediments; it is the same soil, with the difference only which vegetation and the atmospheric influence must necessarily produce.
• The place where the new gulf opened was a pool where the snow and rain-water usually remained for a long time. The explosion took place with a noise like that of thunder, and with the appearance of a mass of fire, in the form of a sheaf, which lasted only about half an hour, accompanied with a thick smoke. The ebullition which threw up a part of the liquid mud lasted till the next day : after which the mud continued running over slowly, and formed six streams, which made their way from the top of the hill to the plain. The body of mud collected by these streams is from three to five archines, that is, from six to ten feet deep, and may be reckoned more than a hundred thousand cubic fathoms-an effusion which approaches the marvellous ! In July, which was the time Mr. Pallas visited the place, the surface of those beds of mud was dry, extremely uneven, and cracked like clayey ground. The gulf that had vomited them was stopped up with the mud which was likewise dry. It was not dangerous to walk over it, but it was frightful, as the horrid bubbling, which was then still heard in the interior of the hill, showed that its bowels were not so tranquil as its surface.
• The mud thus discharged is always a soft clay, of a bluish ashcolour, every where of the same nature, mixed with brilliant sparks of mica, with a small quantity of marly, calcareous, and sandy fragments of schist, which seem torn from the beds directly over the reservoir whence the explosion proceeds. Some cryetals and sparkling laminæ of pyrites, found on these fragments, prove that the heat of the reservoir was not sufficiently powerful to affect the beds which contained those pyrites ; nor was the mud discharged from the gu'f more than lukewarm. The sheaf of fire was probably nothing more than the effect of the phlogistic air, which might have caused the explosion.' P. 257. . · It must be remarked, that the whole of this country is gained from the sea ; and the explosion seems evidently to arise from the expanding vapours, struggling for vent, without the assis
tance of heat. M. Pallas thought it proceeded from the water reaching an old coal-mine which still remained on fire. Some other similar explosions are recorded. The burning springs are sufficiently known ; but our author is not aware of the principle on which the inflammation depends, which is more commonly inflammable air than volatile bitumen: the difference of their nature is however inconsiderable.
When a volcano is extinguished, the fire, it is said, may be expected again to rage if the country be subject to earthquakes; and on this principle-though, as we have said, a doubtful one --our author promises security, or threatens danger.
Maritime and submarine volcanoes are considered at some length; and several curious facts are recorded on these subjects. We can add nothing to the little that we have said on the latter, for little is known. If, however, the submarine volcanoes resemble those on the shores, their eruptions must be of very short duration, and their discharges chiefly aqueous. This our author allows : but he differs from us in supposing the expanded air will throw off the water: we think the air, as it is called, to be produced by the access of the water, and that the steam and water will be ejected together. The subject is however obscure; and the probability may rather be, that these submarine volcanoes are expansions of air independent of heat. We believe many instances are recorded of islands being generated by volcanic fires. One has been formed in the neighbourhood of Iceland within a few years; and another we have lately mentioned, which was raised in the Indian seas, almost under the immediate inspection of two missionaries. The famous Atlantic territory was submerged, as our author thinks, by a volcanic explosion. It was in his opinion situated on the west of Spain, and may have been a part of the American continent.
We have been fuller in our account of this work than we intended. It is indeed a pleasing one, without any essential error. It contains much general information, but is too slight and superficial for the experienced naturalist. As the original is not before us, we cannot speak of the accuracy of the translation. It is, however, free and perspicuous, and appears to be faithful.
ART. V.-The Poetical Works of John Milton, &c. By the Rev.
Henry John Todd, M. A. Continued from p. 254 of the present Volume.)
THE fourth volume contains Paradise Regained and Samson Agonistes. The remarks which Mr. Dunster had subjoined in his edition of Paradise Regained to the end of each book, Mr. Todd
has connected, and prefixed as a preliminary discourse. To these he himself has added remarks on the origin of the poem.
« On this subject the Muses had not been before silent. In our own language, Giles Fletcher had published Christ's Victorie and Triumph, in 1611-an elegant and impressive poem in four parts, of which the second, entitled Christ's Triumph on Earth, describes the Temptation. To this poem, however, the Paradise Regained owes little obligation. Perhaps the Italian Muse might afford a hint. In the following sacred poem, consisting of ten books, “ La Humanita del Figlivolo di Dio. In ottaua rima, per Theofilo Fo. lengo, Mantoano. Venegia, 1533,4°. the fourth book treats largely of the temptation ; from which I will cite the descriptive scene, after the devil has tempted our Lord, and has been rebuked with the reply “ Thou shalt worship the Lord thy God, &c.”
“ Al suon di tanta, et tal sententia un grido
Per suo non già, ma ben per nostro merto.”
“ Ecce per obscuræ tenebrosa crepuscula noctis
Obtulit ignoti se noua forma viri.
Vtque solent, raso vertice tonsus erat.”
“ His actis, deserta petit spelca ferarum : Hic inter vastas rupes, atque horrida lustra,