THE CAMPIDANO.
Perhaps the idea of illimitable extent is better conveyed by the lithographic sketch, No. 8, in which the level, not being interrupted by the intersection of a mountain ridge, as in the former, vanishes in distance. But the termination of the plain in the woodcut is only apparent as, winding round the base of the mountains, the level is still continued though lost to sight. It is not however intended to intimate that these Sardinian plains can at all vie with the great continental levels in various quarters of the globe, the immensity of which occurred to my mind, and some of them to my recollection, when remarking on the impressions such scenes produce on the traveller's sensations. The most extensive of the Sardinian Campidani is only fifty miles in length, and they are all of far less breadth. Their effect is therefore only comparative, but being proportioned to the scale of other surrounding objects, to the area of the insular surface, and the limited height and extent of the mountain ranges, they produce a proportionate effect; but that, as it has been already remarked, is sufficiently striking.
Some brief details of these interesting features in Sardinian scenery—the larger of which are termed Campidani, and the secondary Campi—will be fitly combined with a general sketch of the geological formations of the island; as we are now approaching the same standing point, the central districts, from which we took occasion to review the orology of Corsica. It was then remarked that the mountain systems of the two islands are of similar character and were formerly united; of which there is evidence in the rocky islets scattered from one coast to the other, across the Straits of Bonifacio.[55] Sardinia, however, though apparently a continuation of Corsica, is essentially different in its physical aspect; the elevations being less, the plains more extensive and fertile, its mineralogical riches far more varied, and volcanic action on a large scale being traced throughout the island, while few vestiges of it are discovered in Corsica.
While these sheets have been passing through the press, General Alberto de la Marmora has published two volumes in continuation of his “Voyages en Sardaigne,” devoted exclusively, with an accompanying Atlas, to the geology of the island; a work of the greatest scientific value, from the high character of the author, and the time he has zealously spent in his researches, but too elaborate for any attempt to reduce its details within the compass or the scope of these pages. Our brief sketch must be confined to a few general remarks derived from La Marmora's former volumes, and Captain Smyth's very accurate account of Sardinia; availing ourselves also of Mr. Warre Tyndale's digest of these accounts, and giving some results of our own limited observation.
The principal chain of primitive mountains trends from north to south, extending through the districts of Gallura, Barbagia, Ogliastra, and Budui, along the whole eastern coast of the island. This range consists of granite, with ramifications of schist, and large masses of quartz, mica, and felspar. It is intersected by transverse ranges, and by plains and valleys partly formed by volcanic agency; indeed, the connection between the Gallura group and that of Barbagia is entirely cut off by the great plain of Ozieri.
The most northerly of the series is the Limbara group. Its highest peak, according to La Marmora 4287 feet, is an entire mass of granite. The Genargentu in the Barbagia range, of the same formation, the highest and most central mountain in Sardinia, has two culminating points of the respective heights of 6230 and 6118 feet. They are covered with snow from September till May, and the inhabitants of Aritzu, who make it an object of traffic, are, I believe, able to continue the supply throughout the year.[56] The Monte Oliena in the central group near Nuoro, 4390 feet high, is calcareous, as are two others, between 2000 and 3000 feet high, in the same chain. It terminates with the Sette Fratelli, prolonged to Cape Carbonaro, the eastern point of the gulf of Cagliari, the highest point of the group, which is entirely granite, being 3142 feet.
We find a detached formation called the Nurra mountains, composed of granite, schist, and primitive limestone, filling the isthmus of the Cape at the north-west extremity of the island, and extending to the little isle of Asinara. The mountains of Sulcis, at the extreme south-west, and terminating in the Capes Teulada and Spartivento, are similarly composed; their highest peaks, the Monte Linas and Severa, being from 3000 to 4000 feet high.
But the most striking geological feature in Sardinia consists in the great extent of the volcanic formations. These, as well as the slighter traces of such action in Corsica, are doubtless connected with the subterranean and submarine fires of which the coasts and islands of the central Mediterranean basin afford so many evidences in active and extinct volcanoes (some of them in activity in the times of Homer, Pindar, and Thucydides), and ranging in a circle from the Roman territory to that of Naples, to the Lipari islands, Sicily, and those forming the subject of our present inquiry. Sardinia has been widely ravaged by internal fires, but at too remote an era to admit of our conjecturing the period. The volcanic action can be traced from Castel Sardo, where it has formed precipices on the northern coast, to the vicinity of Monastir, a distance southward of more than 100 miles; its central focus appearing to have been about half-way between Ales, Milis, and St. Lussurgiu, where, as Captain Smyth remarks, “the phlægrean evidences are particularly abundant.” The action was principally confined to the western side of the island, though, south of Genargentu, the volcanic formations approach the primitive chain, and the rounded hills we remarked in the present rambles, after crossing the Limbara, as far east as Oschiri on the Campo d'Ozieri, are, I doubt not, craters of extinct volcanoes. The flat-topped hill, or truncated cone, figured in the lithograph drawing, No. 8, represents one of them, and, scattered as these verdant cones are over the long sweeps of the Campidani, they formed additional features in the interest with which, as I have already said, we regarded those immense tracts.
From the supposed centre of volcanic action just suggested, it may be traced northward through the districts of Macomer, Bonorva, Giavesu, Keremule, with the hillock on which Ardara stands, and Codrongianus, to its termination in the cliffs of Lungo Sardo. But its most salient feature is the detached group of mountains on the western coast between Macomer and Orestano, which are entirely volcanic. This group has the name of “Monte del Marghine,” in the small map prefixed to Captain Smyth's survey, but I do not find that or any other distinct name attached to it in La Marmora's large “Carta dell'Isola.” The village of St. Lussurgiu is literally built in a crater connected with this group, as is also that of Cuglieri. The highest point, Monte Articu, the summit of Monte Ferro, entirely volcanic, rises 3442 feet above the Mediterranean, and the Trebia Lada, 2723 feet high, is one of the three basaltic feet forming the Trebina, or Tripod, on the summit of Monte Arcuentu, a mountain between Orestano and Ales formed of horizontal layers of basalt. Further south at Nurri, closely approaching the primitive chain, are two hills, called “pizzè-ogheddu,” and “pizzè ogu mannu,” or peaks of the little and great eye, which were certainly ignivomous mouths, and the peasants believe that they still have a subterraneous communication. A volcanic stream has run from them over a calcareous tract, forming an elevated plain nearly 1600 feet above the level of the sea, called, “Sa giara e Serri.” It overlooks Gergei, and is covered with oaks and cork trees, while the northern side of its declivity affords rich pasture. North-west from this place is the “Giara di Gestori,” of similar formation, proceeding from a crater at Ales, but strewed with numerous square masses of stone—principally fragments of obsidian, and trachytic and cellular lava—so as to resemble a city in ruins. At Monastir there is a distinct double crater, now well wooded; and a bridge constructed of fine red trap, with the bold outline of the neighbourhood, render the entrance to the village by the Strada Reale singularly picturesque. The volcanic current, flowing westward from Monastir by Siliqua and Massargiu, again approached the coast towards the southern extremity of Sardinia, extending across the deep gulf of Palmas to the islands of S. Pietro and S. Antonio, which are entirely composed of trachytic rocks. Their bold escarpments arrested our attention on approaching the coast, near Cape Teulada, in one of our excursions to Sardinia.
Plains of lava, called “giare” by the natives, are often found reposing on the large tracts of recent formation, such as those of Sardara, Ploaghe, and other places; and considerable extents of trap and pitchstone are frequently met with on limestone strata, while others, tending fast to decomposition, are incorporated with an earth formed of comminuted lava. Vestiges of craters, though generally ill defined, still exist in the vicinity of Osilo, Florinas, Keremule, St. Lussurgiu, Monastir, &c. Some of these are considered, from their less broken and conical shape, and from the surrounding country consisting of fine red ashes, slaggy lava, scoria, obsidian, and indurated pozzolana, with hills of porphyritic trap,—all lying over tertiary rock,—to have been of a much more recent formation than the others, which in form present a lengthened straggling appearance, and in composition resemble those of Auvergne.