ODER, o'dr. One of the principal rivers of Germany (Map: Germany, F 2). It rises on a southern extension of the Sudetic Mountains, near Olmiitz, in Moravia, and flows in a generally northwest direction through Prussian Silesia, Brandenburg, and Pomerania. It empties into the Stettiner Haff, from which its waters flow into the Baltic Sea through three arms which form the islands of Usedom and Rollin. Its length is 562 miles. Only in its extreme upper course does it flow through a hilly and forested country; for the greater part of its length its banks are low and flat, often marshy, and in some places diversi fied with sand dunes. In its lower course it divides repeatedly into parallel arms. which in the last twenty miles form a long, narrow delta. The river is in shallow, and the current is very swift there are sudden and great variations in volume. Extensive and costly engineering works have been necessary to con fine it to its bed and render it navigable, but in dry summers navigation is still uncertain. The
total navigable length for small vessels is 445 miles, ending at Ratibor, in Southern Silesia. Sea-going vessels can ascend as far as Stettin, at the head of the Stettiner Haff, but the chief port used by ocean commerce is Swinemiinde. on the central outlet into the Baltic. The principal tributary of the Oder is the Warthe, which rises in Poland and nearly equals the main river in size. The chief cities on the Oder are Stettin, Frankfort (Brandenburg), Breslau, and Oppeln. Consult: Der Oderstrom, sein Stronwebiet mind seine wichtigsten :\timfliisse (Berlin, 1S96) ; Briimer, "Die Oder and ihr Gebiet," in Zeitsehrift It konigliehen proussischen 8tutimiselten Bu reaus (Berlin, 18119).