Chap. XXX
Effects of vast Levels as compared with Mountain Scenery.—Sketches of Sardinian Geology.—The primitive Chains and other Formations.—Traces of extensive Volcanic action.—The “Campidani,” or Plains.—Mineral Products.
Vast open plains, such as that described in the preceding chapter, form a singular feature in the physical aspect of the island of Sardinia. There are few travellers, I think, of much experience who, in traversing such tracts of country, have not been struck at one time by the desolation of their depths of solitude, or been pleased, at another, by the glimpses of nomade life, their occasional accompaniments; and who would not be willing to admit that, in their general impressions on the imagination, they sometimes rival even mountain scenery. For if grandeur be one main ingredient in the sublime, when an object such as a seemingly boundless level, or rolling plain, the extent of which the eye is unable to scan, lies before you, when, after long marches, it still appears interminable, the mind is perhaps more impressed with the idea of magnitude than by large masses, however enormous, with defined outlines presented to the view. In the former instance, the imagination is called into play and fills out the picture on a scale corresponding with the actual features, as far as they are subject to observation; but the imagination proverbially adopts an extravagant measure.
One of my friend’s sketches of Campidano scenery, introduced here, cleverly represents the effects produced by great distances on one of these rolling plains.
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.
The tertiary formation lies on the west side of the principal granitic chain, and, besides forming the Campidano and the bases on which the volcanic substances rest, constitutes the hills of Cagliari, Sassari, and Sorso. The tertiary limestone seldom ranges more than 1313 feet above the level of the sea, though at Isili and some other places it is 1542 feet high. La Marmora considers it analogous to the upper tertiary formations found in the south of France, central and southern Italy, Sicily, Malta, the Balearic Islands, and Africa. The plains generally consist of a deep alluvial silt, interspersed with shingly patches, containing boulder stones. Such is the valley of the Liscia, occupying nearly the whole surface from sea to sea towards the northern extremity of the island. This, it may be recollected, we crossed north of the Limbara. Then succeeds the series of Campi or Campidani, properly so called. We have already spoken of the vast plain of Ozieri, terminating in the south-west with its minor branches, the Campi di Mela, St. Lazarus, and Giavesu, to which it spreads transversely from the Gulf of Terranova, on the eastern coast. The bottom of this gulf forms one of the finest harbours in the island, with some trade, but the town of that name is a wretched place, remarkable for its insalubrity and the truculent character of the inhabitants.
On the western side of the island are the small Campi of Anglona, lying round Castel Sardo, and another plain highly cultivated between Sassari and Porto Torres. The largest of these plains on the eastern side of the island is that of Orosei, washed by several rivers having their sources in the neighbouring primitive chain of mountains. Westward of this chain we have the great central plain, which, first surrounding the Gulf of Oristano, extends in an unbroken line, for upwards of fifty miles, to the Gulf of Cagliari. This is generally spoken of as “the Campidano,” without further specification, though its parts are distinguished by local names, such as—di Uras, di Gavino, &c.
The mineral riches of Sardinia were well known to the ancients, and vast excavations, with the remains of a number of foundries, afford ample testimony of the extent of their operations. Tradition asserts that gold was formerly extracted; and there is no doubt that silver was found in considerable quantities, as it is even now procured in assaying the lead. Copper is found near Cape Teulada, and at other places, and in one of the mines beautiful specimens of malachite occur. Iron is very plentifully distributed, but is found principally at the Monte Santo of Cape Teulada, and at Monte Ferru. The richest mine is in the Ogliastra, where the intempérie, however, is so malignant as to preclude the formation of an establishment. Lead is the most abundant of Sardinian ores, and its mines are profusely scattered throughout the islands.
Anthracite has been found, but only that of the Nurra district is fit for working; and the coal, though met with in various places in the secondary formations, and especially in the lower parts of the beds of magnesian limestone, is neither sufficient in quantity nor good enough in quality to be generally used. The granites of the Gallura, as we have already mentioned, were known to the ancients, and highly appreciated in Italy for their beauty and colours. Among the other mineral products may also be mentioned the porphyries of the Limbara, the basalt of Nurri, Gestori, and Serri, the alabaster of Sarcidanu, and the marbles of the Goceano and Monte Raso. Jasper abounds in the trachyte and dolomite, and large blocks, of beautiful variety, are found in some districts. Among the chalcedonies are the sardonyx, agates, and cornelian. The districts from whence the ancients obtained the sardonyx, once held in high repute, are not known, but the vicinity of Bosa abounds in chalcedenous formations. A fine quality of quartz amethyst has been obtained, and also hydrophane, known for its peculiar property of becoming transparent when immersed in water. Good turquoises and garnets are also found, but not frequently. Though there have been so many volcanoes, and selenite, gypsum, lime, and aluminous schist frequently occur, neither sulphur nor rock salt have been discovered, and but very little alum. Mineral springs are numerous, but not much frequented.