PNYX, niks (Lat., from Gk. He fl. A hill and ancient place of assembly, whose exact loca tion is not known, in Athens.
PO (anciently Podus and Eridming). The largest river of Italy, flowing through Piedmont and Lombardy. and along the southern borders of Venetia. It rises on Nonte Viso, in the Cot tian Alps, and (lows in a general easterly direc tion through the great valley between the Alps and the Apennines, emptying into the Adriatic Sea after a course of :390 miles (Nap: Italy, F 3). It falls very rapidly in its extreme upper course, its ultimate sources tieing at a height of 6000 feet. In the lower half of its course, how ever, it is a comparatively sluggish strenin, flow ing over a raised alluvial hod so that its surface is higher than the surrounding country, and its banks have to be protected by dikes, which extend continuously from Cremona to the delta. These levees, however, do not follow the smaller wind ings of the river, but cut across peninsulas, which, though unprotected, are cultivated, hut are suhmerged at every considerable rise of the river. The volume of water diseharged by the river is nearly equal to that of the Rhine. The greater part is received from the Alps, and nearly one half collies from the series of large hikes on the southern slope of the mountains. The principal
tributaries from the left are the Dora Riparia, Dora Raltea, Sesia, the Ticino, the outlet of Lago :Maggiore, the Adda from Lago di Como, the Oglio from Lago d'Iseo, and the Nineio from Lago di Garda; from the right the Po receives the Tanaro, Trebbia, Taro, and Panaro. Since the l'o is fed exclusively by mountain torrents, the quantity of sediment carried by its current is enormous, the absolute quantity being nearly equal to that car ried by the Mississippi. As a result of this the delta of the Po grows with nearly the same ra pidity as that of the great American river; it advances into the Adriatic at the rate of more than 200 feet per year. The delta and the sur rounding country consist of unhealthful marshes, and there are scarcely any towns on the lower course of the river. The chief cities on its banks are (ascending) Cremona, Piacenza. Casale Nonferrato (the head of 337 miles from the mouth), and Turin. The plain of the Po is of great fertility.