right bank of the river in the rocky Kazan defile (separating the Balkans on the south from the Carpathians on the north), where a contemporary commemorative tablet is still conspicuously visible. At Turnu Severin below the end of this famous gorge are the remains of a solid masonry bridge constructed by the same emperor at the period of his Dacian conquests. But since Roman days the central Danube has never formed the boundary of a state; on the contrary it became the route followed from east to west by successive hordes of barbarians—the Huns, Avars, Slavs, Magyars and Turks; while the Franks under Charlemagne, the Bavarians and the Crusaders all marched in the opposite direction towards the east. In more modern days its banks were the scenes of many bloody battles during the Napoleonic Wars. Still more recently it has become the great highway of commerce for central Europe. It has been pointed out by J. G. Kohl (Austria and the Danube, London, 1844) and others that, in consequence of the Danube having been in constant use as the line of passage of migratory hostile tribes, it nowhere forms the boundary between two states from Orsova upwards, and thus it traverses as a central artery Württemberg, Bavaria, Austria and Hungary, while on the other hand various tributaries both north and south, which formed serious obstacles to the march of armies, have become lines of separation between different states. Thus Hungary is separated from Austria by the rivers March and Leitha; the river Enns, for a considerable period the extreme western boundary of the Magyar kingdom, still separates Upper and Lower Austria; the Inn and the Salzach divide Austria from Bavaria, and farther west the Iller separates Bavaria from Württemberg.
The Danube after leaving Donaueschingen flows south-east in the direction of Lake Constance, and below Immendingen a considerable quantity of its waters escapes through subterranean fissures to the river Ach in the Rhine basin. At Gutmadingen it turns to the north-east, which Course. general direction, although with many windings, it maintains as far as Linz. At Tuttlingen it contracts and the hills crowd close to the banks, while ruins of castles crown almost every possible summit. The scenery is wild and beautiful until the river passes Sigmaringen. At Ulm, where the river leaves Württemberg and enters Bavaria, it is joined by a large tributary, the Iller, and from this point becomes navigable downstream for specially constructed boats carrying 100 tons of merchandise. It is here some 78 yds. in breadth, with an average depth of 3 ft. 6 in. Continuing its north-easterly course it passes through Bavaria, gradually widening its channel first at Steppberg, then at Ingolstadt, but finally narrowing again until it reaches Regensburg (height 949 ft.). At this point it changes its direction to the south-east, and passing along the southern slopes of the Bavarian Forest enters Austria at Passau (height 800 ft.). In its passage through Bavaria it receives several important affluents on both banks, notably on the right the Alpine rivers Lech, Isar and Inn, the last of which at the junction near Passau exceeds in volume the waters of the Danube.
From Passau the Danube flows through Austria for a distance of 233 m. Closed in by mountains it flows past Linz in an unbroken stream—below, it expands and divides into many arms until it reaches the famous whirlpool near Grein where its waters unite and flow on in one channel for 40 m., through mountains and narrow passes. Beyond Krems it again divides, forming arms and islands beyond Vienna. The Danube between Linz and Vienna is renowned not only for its picturesque beauty but for the numerous medieval and modern buildings of historical and archaeological interest which crown its banks. The splendid Benedictine monastery of Melk and the ruins of Dürrenstein, the prison of Richard Cœur de Lion, are among the most interesting.
After passing Vienna and the Marchfeld, the Danube (here 316 yds. wide and 429 ft. above sea-level) passes through a defile formed by the lower spurs of the Alps and the Carpathians and enters Hungary at the ruined castle of Theben a little above Pressburg, the old Magyar capital, after leaving which the river passes through the Hungarian plains, receiving several affluents on both sides. It divides into three channels, forming several islands. After passing the fortress of Komárom it loses its easterly course at Vácz (Waitzen), and flows nearly due south for 230 m. down to its junction with the Drave (81 ft. above sea-level), passing in its course Budapest, the capital of Hungary, and farther on Mohács. Below Mohács the Franz Josef canal connects the Danube with the Theiss. After its junction with the Save the Danube follows a south-easterly direction for 200 m. until it is joined on the right bank of the Drave at Belgrade, above which it receives on the left bank the Theiss or Tisz., the largest of its Hungarian affluents. From Belgrade the Danube separates Hungary from Servia. It flows eastward until it has passed through the stupendous Kazan defile, in which its waters (at Semlin 1700 yds. wide and 40 ft. deep) are hemmed in by precipitous rocks to a width of only 162 yds., with a depth of 150 ft. and a tremendous current. Emerging, above Orsova, at a height of 42 ft. above sea-level, it opens to nearly a mile in width and, turning south-eastwards, is again narrowed by its last defile, the Iron Gates, where it passes over the Prigrada rock. The course of the river through Hungary, from Pressburg to Orsova, is some 600 m.
The river now flows south, separating Servia from Rumania down to its junction with the Timok, after which as far as Silistria, a distance of 284 m., it separates Rumania from Bulgaria. The north bank is mostly flat and marshy, whereas the Bulgarian bank is almost continuously crowned by low heights on which are built the considerable towns of Vidin (Widdin), Lom Palanka, Rustchuk and Silistria, all memorable names in Turko-Russian wars. From Silistria the river flows through Rumanian territory and after passing Cernavoda, where it is crossed by a modern railway bridge, it reaches (left bank) the important commercial ports of Braila and Galatz. A few miles east of Galatz the Pruth enters on the left bank, which is thenceforward Russian territory. The Danube flows in a single channel from Galatz for 30 m. to the Ismail Chatal (or fork), where it breaks up into the several branches of the delta. The Kilia branch from this point flows to the north-east past the towns of Ismail and Kilia, and 17 m. below the latter breaks up into another delta discharging by seven channels into the Black Sea. The Tulcea branch flows south-east from the Ismail Chatal, and 7 m. below the town of Tulcea separates into two branches. The St George’s branch, holding a general, though winding, course to the south-east, discharges by two channels into the sea; and the Sulina branch, taking an easterly direction, emerges into the Black Sea 20 m. south of the Ochakov mouth of the Kilia, and 20 m. north of the Kedrilles mouth of the St George.
In 1857 the proportion of discharge by the three branches of the Danube was Sulina 7%, St George’s 30% and Kilia 63%; but in 1905 the relative proportions had altered to Sulina 9%, St George’s 24% and Kilia 67%. The average outflow by the three mouths combined is 236,432 cub. ft. per second. The delta enclosed between the Kilia and St George’s branches, about 1000 sq. m. in area, mainly consists of one large marsh covered with reeds, and intersected by channels, relieved in places by isolated elevations covered with oak, beech and willows, many of them marking the ancient coast-line. On the eastern side of the Kilia delta the coast-line is constantly advancing and the sea becoming shallower, owing to the enormous amount of solid deposits brought down by the river. In time of ordinary flood the Kilia branch with its numerous mouths pours into the sea some 3000 cub. ft. of sand and mud per minute. Its effects are felt as far south as Sulina, and tend to necessitate the farther extension into the sea of the guiding piers of that port.
In the course of the 19th century, more especially during its latter half, much was done to render the Danube more available as a means of communication. In 1816 Austria and Bavaria made arrangements for the common utilization of the upper portion of the river, and since then both Navigation. governments have been liberal in expenditure on its improvement. In 1844 the Ludwigs Canal was constructed by King Louis of Bavaria. It is 110 m. in length and 7 ft. in depth, and connects the Danube at Kelheim (half way between Ulm and Passau) with the Rhine at Mainz by means of the rivers Altmühl, Regnitz and
