The Plains.— The great northern plain is formed by, the level portion of the river basin of the Po in Venetia, Lombardy and Romagna. In middle Italy the larger plains extend along the Tyrrhenian coast in varying width between the Magra and Terracina, and flank the middle and lower banks of the Tiber, the Arno and the Ombrone. In the south these plains are in the classic Campania felice, on the sides of the Garigliano and Volturno, and toward the Adri atic form the tableland of Apulia. In the islands the largest plain is' that of Campidano in Sardinia.
These plains are formed chiefly by alluvial deposits caused by the agency of atmospheric forces and by erosion of the base and flanks of the surrounding mountains and distributed by currents, of water in areas which primarily, at least in certain localities, were seas. We find this in the greatest proportion in the valleys of the Po and Venetia, which geologists assure us were in former days a portion of the present Gulf of Venice, which extended like a deep in dentation as far as. Piedmont.
Mountains.— The mountains of Continental and Peninsular Italy are divided into two sys tems: that of, the Apennines and_ that of the Alps. The island mountains are considered, particularly by geologists, as continuations, to a greater or less extent, of the mainland chains. The system of the Apennines belongs entirely to Italy. This is not the case with the Alps/ which extend for the most part into other countries, as France, Switzerland and Austria Hungary. They form, as has been said, the land boundaries of Italy, not in the sense that Italy terminates at their southern base, al though we consider as geographically Italian — as previously mentioned—all the Alpine re• gions whose streams empty into the river • Po and into the Venetian rivers.
To this belong partly or entirely many of the great Alpine colossi from 11,000, or a little more, to 15,781 feet) such as Mount Viso in the Cotian Alps, the Gran Paradise, in the Gra• tian Alps, Mont Blanc and Monte Rosa, in the Pennine Alps, or Valletian Alps, the Adula (Rheinwaldhorn), in the Lepontine Alps, the Bernina, the Orteles, the Adamello, the Wild spitze in the Rhetian Alps, the Vedretta Mar molata in the Dolomitic, or Cadorine Alps, and many others. And the most important thing to observe is, that in this part of Italy there arise from the great plains of the Po and Venetia numerous valleys, many of which are situated in an almost normal direction to the geograph ical axis of the whole system, and pursue a rel. atively short course from the Italian lowlands to the .heart of the whole mountain region, reaching almost to those long longitudinal, or oblique valleys of the Upper Rhone, the Upper Rhine, the Inn, the Drave, etc., which are
characteristic of the non-Italian Alpine water sheds, and which lead to the flourishing Euro pean countries situated on the slopes of the whole mountain system.
Through this singular conformation, the passes, the cols, the saddles, which are found along this boundary were necessarily destined to become the doors of communication between the inhabitants of either water-shed, with the double difference — serious on account of its advan tages, as on account of its perils — that, in the first place, in the north one can reach these passageways by long valleys of easy ascent, whilst to the south one has to climb a more precipitous ascent. As T. Fischer says, these gateways are adapted rather to enter Italy than to' leave it ; and again, these passes radiate and diverge in three directions from Italy as a cen tre — to the west, north and east'— toward the three principal centres of European population, and these three nations all have on the side of the Mediterranean only one neighbor, whilst Italy, on the north, has to deal with three.
The Apennines.—As for the Apennines, they form geographically, and not geologically; the continuation of the Maritime Alps along the Gulf of Genoa, enclosing on the south Continental Italy. They then turn their axis in an oblique direction from northwest to east, traversing the whole of Peninsular Italy: They form a great curve with the concave por tion toward the Tyrrhenian Sea, and in cen tral Italy they extend their principal masses rather toward the Adriatic, approaching then the Tyrrhenian Sea in southern Italy, i.e., the Campania, the Basilicata and Calabria. Geog raphers now make the dividing point between the Alps and the Apennines the Col di Cadi-i bona, or Altar Pass in the west-northwest of Savona. The. Apennines form neither a single nor a continuous chain; but from the principal branch they separate into several spurs and ramifications, or the main chain spreads out in clusters or groups of mountains with terraces, and noted tablelands, such as those of Aquila, Rieti and Perfugia, or divide into a number of chains more or less parallel to each other. Geologists do not attribute to the proper Apen nines many of the mountains in the western part of the peninsula — which includes a great part of Tuscany, of Latium, of the Campania and some portions of Calabria—the mountains and tablelands of Apulia, the volcanoes and part of 'the Prioritani, in Sicily, all those of Sardinia, of Corsica, of the Tuscan Archipelago and many others. The groups and chains, denied by geologists to the Apennines, are as signed by them to other formations, belonging to an earlier geological period, which makes the geography of Italy assume a very different aspect.