Page:The American Cyclopædia (1879) Volume IX.djvu/461

ITALY 44: Perugia (Trasimeno) in Umbria, and the lakes of Bolsena and Braceiano in the province of Rome. Italy offers a rich and in many respects an almost unexplored field to the geologist. Gran- ite, porphyry, and gneiss are found at both the northern and southern extremities, as well as in the centre. Monte Oorvo and other peaks in the Abruzzi are of compact quartz, which also covers largo tracts in Calabria. Aspromonte on the straits of Messina consists almost exclusively of primitive rocks. The mass of the Apennines is composed of lime- stone, chalk, and sandstone, through which at various points throughout their whole extent masses of serpentine have erupted, or have been injected between the strata. This rock forms an important component of the Ligurian Apennines. Commencing near Savona, and showing itself for a considerable space inland as far as Voltaggio, and toward the sea to Genoa, it forms many detached groups of hills, and ceases to be prominent only at Orbetello, in the province of Grosseto. It also rises in great masses near Bobbio and Fornovo, and between Sassuolo and Modena in the basin of Lombardy. The great dislocations and con- tortions of strata in the Ligurian chain are attributed to the eruption of this rock. Gneiss, mica slate, clay slate, talc slate, and limestone form together the lowest stratified series tilt- ed up by the serpentine; above them lies an assemblage of argillaceous slates, marly sand- stones and slates, sandstones, and limestones; while uppermost are marly limestones and a sandstone called in the country macigno, with impressions of marine plants. Upon these are tertiary deposits in horizontal stratification, of limited extent and in detached spots, on the Mediterranean side, but forming in Piedmont and Lombardy a continuous zone on the north- ern slope of the chain from Ceva to Fornovo. The macigno is the prevailing stratified rock in the northern Apennines ; it contains subordi- nate beds of limestone, but no metallic veins or deposits, and is supposed to extend southward as far as Cortona. In this part of the chain are extensive tracts of crystallized limestone, which extend southward along the shore of the Medi- terranean, forming the brocatello marble of Siena, the hill of San Giuliano near Pisa, and insulated hills at Piombino, Civita Vecchia, and Cape Circollo. .The Alpi Appuane, at the southern end of the Ligurian Apennines and contafhing the Carrara marbles, are composed (according to Hoffmann) of Jura limestone, the crystalline state of which is due to the heat contemporaneous with the eruption of the serpentine. Eastward and southward from Liguria, the Apennines are chiefly composed of limestone ; it forms the Apennines of Tus- ! cany, Romagna, Fabriano, Foligno, and the ! Abruzzi, extending through the provinces of Potenza and Bari to the extremity of Otranto. Throughout the northern portion of the Lom- bard plain limestone is the prevailing rock. Above this limestone, and almost coextensive with it, is chalk with its accompanying rocks ; it stretches along the coast of Genoa and into Parma, crosses Modena and Tuscany, forms to the south a long narrow belt along the E. side of the limestone, and after some partial breaks reaches Cape di Leuca, where its white cliffs form a landmark. In the north of the Nea- politan territory a large oval tract of chalk is enclosed by the limestone. Above chalk and limestone are tertiary sandstones, travertine, and marl, occupying a considerable portion of Tuscany and of central Piedmont, but stretch- ing chiefly in a narrow belt along the E. coast from near Rimini to Monte Gargano ; thence the same band spreads out and is continued to the gulf of Taranto. On the coast of Tuscany and in the Roman territory, particularly in the Pontine Marshes, are found partial tracts form- ed by immense diluvial and alluvial deposits, and covering the preceding strata ; but it is in the plains of Lombardy, on the N. W. shore of the Adriatic, and filling the greater part of the basin of the Po, that these deposits are most conspicuous. Besides these formations, there are in Italy four distinct volcanic districts, dis- tributed from the head of the gulf of Venice to Sicily. The first is that of the Euganean hills, extending from near Padua to Este, and separated from the Alps by the Paduan plain. The next and largest district is in the Ro- man territory, where it forms three remark- able groups, the Monti Albani, with Monte Ca- vo (anc. Mans Albania) ; the Monti Cimini, stretching from the Tiber to Civitii Vecchia ; and on the road from Siena to Rome a group to which belong the lofty volcanic mass of Ra- dicofani, and 4 m. away Monte Amiato, 5,794 ft. above the sea. The lakes of Bolsena, Brac- eiano, Vico, Albano, and Nemi are in this dis- trict, all or most of them the craters of extinct volcanoes. At the foot of Monte Amiato is a hot crystal spring, holding in solution a con- siderable amount of sulphur and carbonate of lime, of which advantage is taken to form casts. The water is allowed to fall in broken showers upon moulds, and the calcareous de- posit hardens into cameos and intaglios of ex- quisite beauty. The Terra di Lavoro or Cam- pania Felice (now province of Caserta) in Naples is the third district, subdivided into several marked groups : the Roccamonfina group to the north of the Campanian plains ; the Phle- graan Fields, embracing the country around Baja and Pozzuoli, together with the neigh- boring islands, and the lakes Averno, Lucrino, Fusaro, and Anagno ; and Mt. Vesuvius. The last volcanic district is in Apulia, having for its centre the huge mass of Monte Volture, and for its highest peak the Pizzuto di Melfi, 4,357 ft. In the widest crater are two small lakes. The pools of Ampsanctus (Le Mofete) are in this district, in a wooded valley south of Tri- gento ; they emit carbonic acid and sulphuret- ted hydrogen. The mineral wealth of Italy has been famed from remote times. In the Col di Tenda are mines of lead and silver, considered