The Piave was formerly supposed to have changed its bed in the same manner as the Isonzo. Below the Capo di Ponte, a wild defile in the Dolomite Alps, the Piave flows towards the south-west, past Belluno, and lower down is joined by the Cordevole. It was, however, supposed that the river originally flowed through the valley of Rai, immediately to the south of the Capo di Ponte, and that the Meschio and Livenzo constituted its lower course. Earthquakes or landslips were supposed to have created a barrier across that valley, and the small lakes still seen there were looked upon as remains of the ancient river bed. But M. de Mortillet has shown that this hypothesis is untenable, for the barrier referred to is merely the moraine of an ancient glacier, and there exist no traces whatever of landslips. [Illustration: Fig. 66.—THE SUPPOSED OLD BED OF THE PIAVE. From the Austrian Staff Map. Scale 1 : 550,000.] At the same time it cannot be doubted that extensive changes have taken place in the basin of the Piave. Thus in 1771 the course of the Cordevole, its most important tributary, was obstructed for a time by a landslip which carried the verdant terraces of Pezza down into the valley. Two villages were destroyed, and two others overwhelmed by the rising floods of the river. [Illustration: VENICE.] [Illustration: Fig. 67.—THE LAGOONS OF VENICE. Scale 1 : 394,000.] The Brenta, which rises in the beautiful Sugana valley of the Tyrol, has at all times been a source of anxiety to the Venetians on account of its irregularities. Formerly it entered the lagoons at Fusina, and its alluvium filled up the canals {207} and infected the air. The Paduans and other inhabitants of the lowlands were anxious to divert it by the most direct course into the lagoons, so as to avoid inundations, whilst the Venetians were solicitous to get rid of a river which threatened to fill up their lagoons and render them insalubrious. These conflicting interests gave rise to numerous wars. The possession of the coast became a question of existence to the Venetians, and no sooner had they obtained it than they set about “regulating” the Lower Brenta. Hy means of two canals, the Brenta Nuova, or Brentone, and the Brenta Nuovissima, the river was conducted right round the lagoons to the port of Brondolo, a few miles to the north of the Adige. But the river, whose course had thus been considerably lengthened, gradually filled up the bed in its upper course, and it was found impossible to {208} confine it within its lateral embankments. They were broken through by the floods no less than twenty times between 1811 and 1859, and, as the channel of the river became more and more choked, a more frequent recurrence of such disasters was naturally expected. It was then resolved to shorten the course of the river to the extent of ten miles, by diverting it into a portion of the lagoon of Chioggia. The danger of irruptions has thus been averted for a time, but the fisheries