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 southwest extremity, the Oglio has a long and winding course through the plain before it finally reaches the Po a few miles above Borgoforte.
The whole of this plain has been formed by the debris swept down from the Alps by the rivers Po, Ticino, Oglio, Adda, Mincio, Adige, Brenta, Piave, Livenza, Tagliamento and Isonzo.
In the former class are the Isere, the Rhone, the Aar, the Ticino, the Tosa, the Hinter (or main) Rhine and the Linth; while in the latter class we have the Durance, the Po, the Reuss, the Vorder and middle branches of the Rhine, the Inn, the Adda, the Oglio and the Adige.
Strictly speaking, we should follow the Reschen Scheideck route down the Adige valley, but as this would include in the Central Alps the Ortler and some other of the highest Tirolese summits, it is best (remembering the artificial character of the division) to draw a line from Nlals southwards either over the Umbrail Pass (the old historical pass) or the Stelvio (wellknown only since the carriage road was built over it in the first quarter of the 19th century) to the head of the Valtellina, and then over the Aprica Pass (as the Bergamasque Alps properly belong to the Central Alps) to the Oglio valley or the Val Camonica, and down that valley to the Lake of Iseo and Brescid.