TIBER (Lat. Tiberis, poetical Thybris; Ital. Tcrcre). The principal river of Central Italy. It rises in Tuscany, at the south of the Monte Film join, in the Province of Arezzo, about thirty miles east of the source of the Arno, at an altitude of more than 3600 feet above 'the level of the sea, and flows toward the south in a winding course, entering the Province of Perugia where it passes through the valley between Perugia and Assisi. it receives the waters of many smaller streams, and at Orte, where it is joined by the Nera (the ancient Nor), it begins to form the boundary between the provinces of Umbria and Rome, encircling Mount Soracte and entering the Campagna Romana. About three miles above Rome it is swelled by the Anio (now Aniene or Teverone). then passes through the city of Rome, where it forms an island, the lnsula Tiberina ( now Isola di San Bartolommeo). and enters the Tyrrhenian Sea about twenty-six miles below.
The total length of the Tiber is 245 miles; its breadth at Rome is about 250 feet. It is a swift running stream, carrying down an ern:411011S amount of alluvial matter, which, in solution, gives the water that yellowish color for which the tlavus Tiberis was renowned. The sediment de posited at the mouth of the Tiber is pushing out the land at the rate of about ten feet a year, so that the ruins of Ostia, the ancient harbor of Rome, are now more than four miles inland. The
delta is formed of two mouths: the if ieino, orig ina Ily a channel dug by Trajan for his harbor (Portus Traiani), now the larger and navigable branch, and the finmara, now almost choked by sand banks; and these inclose the Isola Sacra. a desolate and unhealthy island once sacred to Venus. The Tiber is navigable by small steamers as far as Rome, and by smaller craft as far as Orte, about sixty wiles from its mouth. It is subject to frequent and often disastrous inun dations, of which the ancient writers have re corded no less than twenty-three. Among the more famous floods are that mentioned by Horace (Odes, 1. 2). that of 1598, when the water at Rome rose feet, and that of 1900, when it reached a flood-height of almost 54 feet. To remedy this evil, the Government. beginning in 1876, has constructed massive embankments at Rome, at the expense of more than $25,000,000; but already the carefully planned work has proved defective. The stream on the north of the Tiber island has become clogged with sand, and in the flood of 1900 fully a quarter of a mile of the south embankment was carried away by the water.
Consult : S. M. Smith, The Tiber and Its Tribu taries (London, 1877) : Nardneci, Saggio di Bib liografia del Terere (Rome, 1876).