where the sea-bottom sinks rapidly down towards the eastern basin of the Mediterranean, steep rocky coasts prevail except opposite the plain of Catania. In the northern half of this coast the lava streams of Mount Etna stand out for a distance of about 20 M. in a line of bold cliffs and promontories. At various points on the east, north and west coasts there are evidences of a rise of the land having taken place within historical times, at Trapani on the west coast even within the 19th century. As in the rest of the Mediterranean, tides are scarcely observable; but at several points on the west and south coasts a curious oscillation in the level of the waters, known to the natives as the marrobbio (or marobia), is sometimes noticed, and is said to be always preceded by certain atmospheric signs. This consists in a sudden rise of the sea-level, occasionally to the height of 3 ft., sometimes occurring only once, sometimes repeated at intervals of a minute for two hours, or even, at Mazzara, where it is most frequently observed, for twenty-four hours together.
The surface of Sicily lies for the most part more than 500 ft. above the level of the sea. Caltanissetta, which occupies the middle point in elevation as well as in respect of geographical situation, stands 1900 ft. above sea-level. Considerable mountains occur only in the north, where the lower slopes of all the heights form one continuous series of olive-yards and orangeries. Of the rest of the island the greater part forms a plateau varying in elevation and mostly covered with wheat-fields. The only plain of any great extent is that of Catania, watered by the Simeto, in the east; to the north of this plain the active volcano of Etna rises with an exceedingly gentle slope to the height of 10,868 ft. from a base 400 sq. m. in extent. This is the highest elevation of the island. The steep and narrow crystalline ridge which trends north-eastwards, and is known to geographers by the name of the Peloritan Mountains, does not reach 4000 ft. The Nebrodian Mountains, a limestone range connected with the Peloritan range and having an east and west trend, rise to a somewhat greater height, and farther west, about the middle of the north coast, the Madonie (the only one of the groups mentioned which has a native name) culminate at the height of nearly 6500 ft. From the western end of the Nebrodian Mountains a lower range (in some places under 1500 ft. in height) winds on the whole south-eastwards in the direction of Cape Passaro. With the exception of the Simeto, the principal perennial streams—the Salso, the Platani and the Belice—enter the sea on the south coast.
Geology.[1]—In general, the older beds occur along the northern coast, and progressively newer and newer beds are found towards the south. Folding, however, has brought some of the older beds to the surface in the hills which lie to the north and north-east of Sciacca. The Monti Peloritani at the north-eastern extremity of the island consists of gneiss and crystalline schists; but with this exception the whole of Sicily is formed of Mesozoic and later deposits, the Tertiary beds covering by far the greater part. Triassic rocks form a discontinuous band along the northern coast, and are especially well developed in the neighbourhood of Palermo. They rise again to the surface in the southern part of the island, in the hills which lie to the north of Sciacca and Bivona. In both areas they are accompanied by Jurassic, and occasionally by Cretaceous, beds; but of the latter there are only a few small patches. In the southeastern part of the island there are also a few very small outcrops of Mesozoic beds. The Eocene and Oligocene form a broad belt along the northern coast, very much more continuous than the Mesozoic band, and from this belt a branch extends southwards to Sciacca. Another patch of considerable size lies to the east of Piazza-Armerina. Miocene and Pliocene deposits cover nearly the whole of the country south of a line drawn from Etna to Marsala; and there is also a considerable Miocene area in the north about Mistretta. Volcanic lavas and ashes of a recent geological period form not only the whole of Etna but also a large part of the Monti Iblei in the south. Small patches occur also at Pachino and in the hills north of Sciacca.
Climate.—The climate of Sicily resembles that of the other lands in the extreme south of Europe. As regards temperature, it has the warm and equable character which belongs to most of the Mediterranean region. At Palermo (where continuous observations have been made since 1791) the range of temperature between the mean of the coldest and that of the hottest month is little greater than at Greenwich. The mean temperature of January (51½° F.) is nearly as high as that of October in the south of England, that of July (77° F.) about 13° warmer than the corresponding month at Greenwich. In only seven of the thirty years, 1871-1900, was the thermometer observed to sink below the freezing-point; frost thus occurs in the island even on the low grounds, though never for more than a few hours. On the coast snow is seldom seen, but it does fall occasionally. On the Madonie it lies till June, on Etna till July. The annual rainfall except on the higher mountains does not reach 30 in., and, as in other parts of the extreme south of Europe, it occurs chiefly in the winter months, while the three months (June, July and August) are almost quite dry. During these months the whole rainfall does not exceed 2 in., except on the slopes of the mountains in the north-east. Hence most of the streams dry up in summer. The chief scourge is the sirocco, which is experienced in its most characteristic form on the north coast, as an oppressive, parching, hot, dry wind, blowing strongly and steadily from the south, the atmosphere remaining through the whole period of its duration leaden-coloured and hazy in consequence of the presence of immense quantities of reddish dust. It occurs most frequently in April, and then in May and September, but no month is entirely free from it. Three days are the longest period for which it lasts. The same name is sometimes applied to a moist and not very hot, but yet oppressive, south-east wind which blows from time to time on the east coast. Malaria occurs in some parts of the island.
Flora.—The flora of Sicily is remarkable for its wealth of species; but, comparing Sicily with other islands that have been long separated from the mainland, the number of endemic species is not great. The orders most abundantly represented are the Compositae, Cruciferae, Labiatae, Caryophyllaceae and Scrophulariaceae. The Rosaceae are also abundantly represented, and among them are numerous species of the rose. The general aspect of the vegetation of Sicily, however, has been greatly affected, as in other parts of the Mediterranean, by the introduction of plants within historical times. Being more densely populated than any other large Mediterranean island, and having its population dependent chiefly on the products of the soil, it is necessarily more extensively cultivated than any other of the larger islands referred to, and many of the objects of cultivation are not originally natives of, the island. Not to mention the olive, which must have been introduced at a remote period, all the members of the orange tribe, the agave and the prickly pear, as well as other plants highly characteristic of Sicilian scenery, have been introduced since the beginning of the Christian era. With respect to vegetation and cultivation three zones may be distinguished. The first reaches to about 1600 ft. above sea-level, the upper limit of the members of the orange tribe; the second ascends to about 3300 ft., the limit of the growth of wheat, the vine and the hardier evergreens; and the third, that of forests, reaches from about 3300 ft. upwards. But it is not merely height that determines the general character of the vegetation. The cultivated trees of Sicily mostly demand such an amount of moisture as can be obtained only on the mountain slopes, and it is worthy of notice that the structure of the mountains is peculiarly favourable to the supply of this want. The limestones of which they are mostly composed act like a sponge, absorbing the rain-water through their innumerable pores and fissures, and thus storing it up in the interior, afterwards to allow it to well forth in springs at various elevations lower down. In this way the irrigation which is absolutely indispensable for the members of the orange tribe during the dry season is greatly facilitated, and even those trees for which irrigation is not so indispensable receive a more ample supply of moisture during the rainy season. Hence it is that, while the plain of Catania is almost treeless and tree-cultivation is comparatively limited in the west and south, where the extent of land under 1600 ft. is considerable, the whole of the north and north-east coast from the Bay of Castellammare round to Catania is an endless succession of orchards, in which oranges, citrons and lemons alternate with olives, almonds, pomegranates, figs, carob trees, pistachios, mulberries and vines. The limit in height of the olive is about 2700 ft., and that of the vine about 3500 ft. The lemon is really grown upon a bitter orange tree, grafted to bear the lemon. A considerable silk production depends on the cultivation of the mulberry in the neighbourhood of Messina and Catania. Among other trees and shrubs may be mentioned the sumach, the date-palm, the plantain, various bamboos, cycads and the dwarf-palm, the last of which grows in some parts of Sicily more profusely than anywhere else, and in the desolate region in the south-west yields almost the only vegetable product of importance. The Arundo Donax, the tallest of European grasses, is largely grown for vine-stakes.
Population.—The area and population of the several provinces are shown in the table on the next page. Thus between 1881 and 1901 the population increased at the rate of 20.5%. The average density is extremely high for a country which lives almost exclusively by agriculture, and is much higher than the average for Italy in general, 293 per sq. m. In 1905 the population was 3,568,124, the rate of increase being only 4.4% per annum; the low rate is due to emigration.
- ↑ A general account of the geology of the island will be found in L. Baldacci, Descrizione geologica dell' isola di Sicilia (Rome, 1886), with map. For fuller and later information reference should be made to the publications of the Reale Comitato Geologico d'Italia.
