More important are the rivers that descend from the main chain of the Graian and Pennine Alps and join the Po on its left bank. Of these the Dora (called for distinction’s sake Dora Riparia), which unites with the greater river just below Turin, has its source in the Mont Genèvre, and flows past Susa at the foot of the Mont Cenis. Next comes the Stura, which rises in the glaciers of the Roche Melon; then the Orca, flowing through the Val di Locana; and then the Dora Baltea, one of the greatest of all the Alpine tributaries of the Po, which has its source in the glaciers of Mont Blanc, above Courmayeur, and thence descends through the Val d’Aosta for about 70 m. till it enters the plain at Ivrea, and, after flowing about 20 m. more, joins the Po a few miles below Chivasso. This great valley—one of the most considerable on the southern side of the Alps—has attracted special attention, in ancient as well as modern times, from its leading to two of the most frequented passes across the great mountain chain—the Great and the Little St Bernard—the former diverging at Aosta, and crossing the main ridges to the north into the valley of the Rhone, the other following a more westerly direction into Savoy. Below Aosta also the Dora Baltea receives several considerable tributaries, which descend from the glaciers between Mont Blanc and Monte Rosa.
About 25 m. below its confluence with the Dora, the Po receives the Sesia, also a large river, which has its source above Alagna at the southern foot of Monte Rosa, and after flowing by Varallo and Vercelli falls into the Po about 14 m. below the latter city. About 30 m. east of this confluence—in the course of which the Po makes a great bend south to Valenza, and then returns again to the northward—it is joined by the Ticino, a large and rapid river, which brings with it the outflow of Lago Maggiore and all the waters that flow into it. Of these the Ticino itself has its source about 10 m. above Airolo at the foot of the St Gotthard, and after flowing above 36 m. through the Val Leventina to Bellinzona (where it is joined by the Moësa bringing down the waters of the Val Misocco) enters the lake through a marshy plain at Magadino, about 10 m. distant. On the west side of the lake the Toccia or Tosa descends from the pass of the Gries nearly due south to Domodossola, where it receives the waters of the Doveria from the Simplon, and a few miles lower down those of the Val d’Anzasca from the foot of Monte Rosa, and 12 m. farther has its outlet into the lake between Baveno and Pallanza. The Lago Maggiore is also the receptacle of the waters of the Lago di Lugano on the east and the Lago d’Orta on the west.
The next great affluent of the Po, the Adda, forms the outflow of the Lake of Como, and has also its sources in the Alps, above Bormio, whence it flows through the broad and fertile valley of the Valtellina for more than 65 m. till it enters the lake near Colico. The Adda in this part of its course has a direction almost due east to west; but at the point where it reaches the lake, the Liro descends the valley of S. Giacomo, which runs nearly north and south from the pass of the Splügen, thus affording one of the most direct lines of communication across the Alps. The Adda flows out of the lake at its south-eastern extremity at Lecco, and has thence a course through the plain of above 70 m. till it enters the Po between Piacenza and Cremona. It flows by Lodi and Pizzighettone, and receives the waters of the Brembo, descending from the Val Brembana, and the Serio from the Val Seriana above Bergamo. The Oglio, a more considerable stream than either of the last two, rises in the Monte Tonale above Edolo, and descends through the Val Camonica to Lovere, where it expands into a large lake, called Iseo from the town of that name on its southern shore. Issuing thence at its south-west extremity, the Oglio has a long and winding course through the plain before it finally reaches the Po a few miles above Borgoforte. In this lower part it receives the smaller streams of the Mella, which flows by Brescia, and the Chiese, which proceeds from the small Lago d’Idro, between the Lago d’Iseo and that of Garda.
The last of the great tributaries of the Po is the Mincio, which flows from the Lago di Garda, and has a course of about 40 m. from Peschiera, where it issues from the lake at its south-eastern angle, till it joins the Po. About 12 m. above the confluence it passes under the walls of Mantua, and expands into a broad lake-like reach so as entirely to encircle that city. Notwithstanding its extent, the Lago di Garda is not fed by the snows of the high Alps, nor is the stream which enters it at its northern extremity (at Riva) commonly known as the Mincio, though forming the main source of that river, but is termed the Sarca; it rises at the foot of Monte Tonale.
The Adige, formed by the junction of two streams—the Etsch or Adige proper and the Eisak, both of which belong to Tirol rather than to Italy—descends as far as Verona, where it enters the great plain, with a course from north to south nearly parallel to the rivers last described, and would seem likely to discharge its waters into those of the Po, but below Legnago it turns eastward and runs parallel to the Po for about 40 m., entering the Adriatic by an independent mouth about 8 m. from the northern outlet of the greater stream. The waters of the two rivers have, however, been made to communicate by artificial cuts and canals in more than one place.
The Po itself, which is here a very large stream, with an average width of 400 to 600 yds., continues to flow with an undivided mass of waters as far as Sta Maria di Ariano, where it parts into two arms, known as the Po di Maestra and Po di Goro, and these again are subdivided into several other branches, forming a delta above 20 m. in width from north to south. The point of bifurcation, at present about 25 m. from the sea, was formerly much farther inland, more than 10 m. west of Ferrara, where a small arm of the river, still called the Po di Ferrara, branches from the main stream. Previous to the year 1154 this channel was the main stream, and the two small branches into which it subdivides, called the Po di Volano and Po di Primaro, were in early times the two main outlets of the river. The southernmost of these, the Po di Primaro, enters the Adriatic about 12 m. north of Ravenna, so that if these two arms be included, the delta of the Po extends about 36 m. from south to north. The whole course of the river, including its windings, is estimated at about 450 m.
Besides the delta of the Po and the large marshy tracts which it forms, there exist on both sides of it extensive lagoons of salt water, generally separated from the Adriatic by narrow strips of sand or embankments, partly natural and partly artificial, but having openings which admit the influx and efflux of the sea-water, and serve as ports for communication with the mainland. The best known and the most extensive of these lagoons is that in which Venice is situated, which extends from Torcello in the north to Chioggia and Brondolo in the south, a distance of above 40 m.; but they were formerly much more extensive, and afforded a continuous means of internal navigation, by what were called “the Seven Seas” (Septem Maria), from Ravenna to Altinum, a few miles north of Torcello. That city, like Ravenna, originally stood in the midst of a lagoon; and the coast east of it to near Monfalcone, where it meets the mountains, is occupied by similar expanses of water, which are, however, becoming gradually converted into dry land.
The tract adjoining this long line of lagoons is, like the basin of the Po, a broad expanse of perfectly level alluvial plain, extending from the Adige eastwards to the Carnic Alps, where they approach close to the Adriatic between Aquileia and Trieste, and northwards to the foot of the great chain, which here sweeps round in a semicircle from the neighbourhood of Vicenza to that of Aquileia. The space thus included was known in ancient times as Venetia, a name applied in the middle ages to the well-known city; the eastern portion of it became known in the middle ages as the Frioul or Friuli.
Returning to the south of the Po, the tributaries of that river on its right bank below the Tanaro are very inferior in volume and importance to those from the north. Flowing from the Ligurian Apennines, which never attain the limit of perpetual snow, they generally dwindle in summer into insignificant streams. Beginning from the Tanaro, the principal of them are—(1) the Scrivia, a small but rapid stream flowing from the Apennines at the back of Genoa; (2) the Trebbia, a much larger river, though of the same torrent-like character, which rises near Torriglia within 20 m. of Genoa, flows by Bobbio, and joins the Po a few miles above Piacenza; (3) the Nure, a few miles east of the preceding; (4) the Taro, a more considerable stream; (5) the Parma, flowing by the city of the same name; (6) the Enza; (7) the Secchia, which flows by Modena; (8) the Panaro, a few miles to the east of that city; (9) the Reno, which flows by Bologna, but instead of holding its course till it discharges its waters into the Po, as it did in Roman times, is turned aside by an artificial channel into the Po di Primaro. The other small streams east of this—of which the most considerable are the Solaro, the Santerno, flowing by Imola, the Lamone by Faenza, the Montone by Forlì, all in Roman times tributaries of the Po—have their outlet in like manner into the Po di Primaro, or by artificial mouths into the Adriatic between Ravenna and Rimini. The river Marecchia, which enters the sea immediately north of Rimini, may be considered as the natural limit of Northern Italy. It was adopted by Augustus as the boundary of Gallia Cispadana; the far-famed Rubicon was a trifling stream a few miles farther north, now called Fiumicino. The Savio is the only other stream of any importance which has always flowed directly into the Adriatic from this side of the Tuscan Apennines.
The narrow strip of coast-land between the Maritime Alps, the Apennines and the sea—called in ancient times Liguria, and now known as the Riviera of Genoa—is throughout its extent, from Nice to Genoa on the one side, and from Genoa to Spezia on the other, almost wholly mountainous. It is occupied by the branches and offshoots of the mountain ranges which separate it from the great plain to the north, and send down their lateral ridges close to the water’s edge, leaving only in places a few square miles of level plains at the mouths of the rivers and openings of the valleys. The district is by no means devoid of fertility, the steep slopes facing the south enjoying so fine a climate as to render them very favourable for the | growth of fruit trees, especially the olive, which is cultivated in terraces to a considerable height up the face of the mountains, while the openings of the valleys are generally occupied by towns or villages, some of which have become favourite winter resorts.