One of the smallest of these ice streams, that which descended from the mountains of Tenda in the direction of Cuneo, had a length of thirty miles. That which brought down the ice of Mont Genèvre, Mont Tabor, and Mont Cenis had twice that length, and its moraines formed a veritable amphitheatre of hills, locally known as _regione alla pietre_, or stony region. Farther north the streams of ice descending from the Pennine Alps between the Grand Paradis and Mont Blanc united in a single stream eighty miles in length, and spread over the plain far beyond Ivrea. The alluvial accumulation of this ancient glacier rises 1,100 and even 2,130 feet above the valley through which the Dora Baltea now flows. One of its lateral moraines, known as the _Serra d’Ivrea_, forms a regular rampart to the east of the river, eighteen miles in extent. Its slopes are now covered with chestnuts. The western ravine (Colle di Brossa) is less prominent, because it is inferior in height; but the frontal ravine, forming a complete demicircle, can still be traced readily. In the débris accumulated at the foot of this ancient glacier, rocks derived from Mont Blanc are mixed with others brought down from Mont Cervin. And yet it was but a dwarf when compared with the ancient twin glacier of the Ticino and the Adda, which extended from the Simplon to the Stelvio, filled up the cavities now occupied by the Lago Maggiore {196} and the Lake of Como, sent a lateral branch to the tortuous bed of the Lake of Lugano, and finally, after a course of from 100 to 120 miles, debouched upon the plain of Lombardy. The glacier of the Oglio was small in comparison with it, but it was exceeded by that of the Adige, the most considerable of all on the southern slope of the Alps. This river of ice, from the mountains of the Oetzthal, where it originated, to its terminal moraine to the north of Mantua, had a length of 175 miles. One of its branches descended towards the east, down the valley of the Drave, as far as where the town of Klagenfurt now stands. Its main stream filled up the cavity of the Lake of Garda, pushing along a formidable rampart of elevated moraines. [Illustration: Fig. 57.—THE SERRA OF IVREA AND THE ANCIENT GLACIER LAKES OF THE DORA. From the Sardinian Staff Map. Scale 1 : 250,000] The hand of man is scarcely able to make an impression upon the vast accumulations heaped up by the action of the glaciers. The hills of Solferino, of Cavriana, and Somma Campagna, so often named in connection with battles, are nothing but débris brought down from the flanks of the Alps, and they were much higher formerly than they are now. {197}