HYDROGRAPHY. Italy has many streams, al though it has only one great river, the l'o. The most important streams, the l'o and the Adige, flow into the Adriatic Sea. The Po is fed on one side by the snows of the Alps, on the other by the heavy rains of the Apennines, and drains an area of 27,000 square miles, of which nearly 11,000 are level, and, indeed, almost flat. Its course marks the line at which the sediment and d•ris from the Alps meet the sediment and debris from tho Apennines. The Po is navigable to Turin, and with its tributaries affords about 600 miles of navigation. The Adige enters Italy from Tyrol, and flows eastward to the Adriatic. The beds of both these rivers arc constantly being elevated by the boulders and alluvial deposits brought down from the mountains. The rivers of the Peninsula are of little importance for navigation or industry. The beds of most of them are dry in slimmer, so that they cannot be relied upon for wate•-powe•. The most impor tant among them are the Arno, which rises in the Apennines and flows west past Florence and Pisa through a lovely and well-cultivated valley.
It has a short course of only 150 miles. The Tiber rises not far from the sources of the Arno, the two rivers being connected by a canal through the tributary called the Chiana, whose waters flow partly into the Arno and partly into the Tiber. The canal system is thoroughly developed in the basin of the Po, and is utilized not only for transportation, but also for the irrigation of hay and rice, so that the farmer in the great plain is almost independent of rain. There are many lakes where the mountains merge into the great plain; also a considerable number in the Peninsula.some of which are crater lakes. The chief lakes of Northern Italy are. in the order of their size, Garda, and Como. Each of them sends down a large tributary to the Po. Lago di Garda covers an area of 140 square miles, and is very deep. Lago Maggiore is longer than Como, but not so large as Garda ; a part of this lake is in Switzerland. Lago di Como is one of the loveliest lakes in the world. Other considerable lakes are Lugano and Iseo.