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have myself seen specimens from that province, and probably from the same locality, in the possession of Professor Schuster at Buda, which from their scoriform aspect I should judge to be of modern formation.

Dr. Boué also informs me, that between Ober-Pullendorf and Stoop, near Güns in Hungary, south of the lake of Neusiedel, is a flat conical hill about 100 feet in height, half a league in its greatest diameter, and a quarter of a league in its smallest, which rises from the midst of the upper tertiary deposits, or amongst the marly beds lying above the blue shelly marl common to Austria and the Apennines. The rock itself is composed of a blackish or greyish felspathic basalt, which is sometimes compact, and contains oval nodules, partly of mamillary or botryoidal iron ore, and partly of arragonite; sometimes very porous, and with the cavities either entirely empty, are coated with globules of sphæro-siderite.

The direction of the cells is from east-north-east to westsouth-west, and the same is the direction of the range itself. It is decidedly a tertiary basaltic cone, having its base only covered by recent marls.

On the Volcanic Rocks of Styria.

On my way from Vienna to Italy I deviated a little from the direct road, in order to lock at some rocks of a volcanic nature that occur near Friedau in Styria, a little to the south-east of Gräbz, of which the only account which has been published, is one by Von Buch, in the Transactions of the Academy of Berlin.*

The formation in question may be briefly stated, as consisting of a central nucleus of trachyte, which consitutes the lofty conical hill called the Gleichenburg, round which on all sides are mantle-shaped strata of volcanic tuff, alternating with beds belonging apparently to the tertiary class.

* Vide Leop. von Buch in der Abh, der physical Classe der Kön. Akademie zu Berlin, 1818.

This tuff consists in general of a congeries of very minute fragments of volcanic matter, which seem to have been immediately ejected from the volcano, mixed up and loosely agglutinated with small quartzy pebbles. In the midst of it are fragments of cellular and compact basaltic lava, sometimes containing nests of olivine. Masses of the same substance of a globular form, not imbedded in any matrix, are found also distributed amongst the tuff. Specimens of augite, and of a substance looking like altered granite likewise occur. The tuff becoming more and more mixed with particles of clay and sand, passes at length into a loamy earth, at first dark, and afterwards, where it is unmixed with volcanic matter, of an ash-grey colour. The constituents are in a state of very fine divison, and a number of minute specks of silvery mica impart a sparkling lustre to the general mass.

Besides this, which looks like a bed of silt deposited tranquilly at the bottom of a lake, we find, at a somewhat greater distance from the central trachyte, strata of limestone, full of shells, belonging to the recent order of deposits, and especially abounding in that minute fossil, the miliolite, which imparts to the stone an oolitic appearance. At a village called Khelig, a little to the south of the former locality, I observed that the tuff, which here contained decided scoriæ, was superimposed on a rock which no wise differed from ordinary basalt, but in the existence of minute internal pores. It formed a number of concentric iamellar concretions, of which the external have become decomposed, whilst the internal retain their solidity. The exterior surface of the balls is coated with asphaltum. The whole rests upon a bed of marl without any traces of volcanic

matter.

Two hypotheses present themselves with respect to the age of the trachyte of the Gleichenburg; for it may either be said, that having been first thrown up by volcanic action, the beds of tuff and of marl collected by degrees around its base; or that after the latter had been formed in a position

approaching to the horizontal, the rock of the Gleichenburg, being forced up through the midst of them, imparted the inclination which they are now seen to possess.

For my own part I am most disposed to adopt the latter opinion, on the same ground on which I assented to M. Bertrand Roux's ideas with respect to the rock of the Mount Mezen; for it seems probable that if the trachyte had been formed in the first instance, fragments of it ought to appear intermixed with the other materials of the tuff, which I did not discover to be the case. The inclination likewise possessed by the strata of tuff seems to me too considerable to be consistent with the former hypothesis, but accords very well with the latter.

The following sketch may give an idea of the disposition of the central trachyte.

Where a. & b. are alternating beds of tuff and loam or sand, C is the trachyte, and D a valley of denudation separating the two rocks.

EUGANEAN HILLS.

On entering Italy by the side of Venice, we have not far to go before we meet with a very extensive and interesting volcanic district.

To the south of Padua lie the Euganean hills, an isolated tract of high ground in the midst of a level country, consisting of a trachytic formation, not unlike that of Hungary, which, from its cellular structure in some cases, and its semi-vitreous aspect in others, would at once be taken for a volcanic product. Like the formation too of the latter country, it consists of several kinds of rock, which however are so allied, and so connected by mutual passages, as to shew that they have been all derived from a modification of the same process.

The most characteristic variety is a rock of an ash-grey colour and uneven fracture, very like the porphyry of Mont Dor, or the first species of Beudant's trachyte formation, (Monselice). It contains numerous crystals of glassy felspar, sometimes decomposed, sometimes fresh, and occasional specks of black mica, which is also accumulated in nests, the several parts of which have a slaty structure, like that of mica slate. Crystals of augite are also found under the same circumstances. Associated with this is a rock possessing a splintery fracture, waxy lustre, and vitreous appearance, which may be called an hornstone porphyry. Some varieties are cellular, and contain infiltrations of quartz and chalcedony, like the millstone trachyte of Hungary. Others approach very nearly to the characters of pearlstone, presenting, together with the vitreous aspect of that substance, an approach to a similar concentric arrangement. (Monte Siave). In these cases the crystals of glassy felspar, which distinguish true trachyte, are either absent, or very rarely

occur.

This formation is associated at Monte Venda with basalt, the relation of which to the trachyte is as obscure as in the parallel case of the Siebengebirge. It is also surrounded,

H

EUGANEAN HILLS.

at Castelletto, by strata of tuff, and of pumiceous conglomerate, in a manner analogous to what I have described as taking place near the Gleichenburg in Styria, but disposed more vertically.

In some parts a conglomerate or breccia occurs, (Monte Nuovo) which seems to be principally made up of the hornstone above described, intermixed with a white powdery siliceous substance, which fills up the interstices. The whole of this mass might be imagined, as well from its vitreous appearance, as from the intimate union of its parts, to have been consolidated by fusion, or at least by the action of heat.

The trachyte of the Euganean hills rests upon a calcareous rock, which appears to correspond with the chalk of Great Britain. It is called Scaglia, from its slaty structure, being disposed in thin horizontal layers. Its colour is commonly white, now and then with a shade of red, and its compactness usually is quite equal to that of our hardest chalk, though softer varieties are sometimes met with.

The points however chiefly to be insisted on, as establishing the identity of the two formations, are, the kidneyshaped masses of flint disposed in beds throughout the Scaglia, as in the chalk of England, and the nature of the. petrifactions that occur in it, which, from the list given in the Abbé Maraschini's late work, appear to consist of ammonites, terebratulites, and various species of the echinus family; viz. the echinoneus, galerites, ananchytes, spatangus, cidaris, nucleolites, and echinus proper, of Lamarck.

By comparing this list with the one given in Messrs.. Conybeare and Phillips' Geology of England and Wales, p. 73, it will be seen, that the analogy between the two for mations is in this respect considerable.

I know not whether the redness and brittleness of the flints in a part of the rock which lies near the trachyte, not

*Sulle Formazioni delle Rocce del Vicentino. Padova, 1824. p. 122.

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