Rhine (Ger. Rhein; Dutch, Rijn or Ryn; Fr. Rhin; anc. Rhenus), one of the principal rivers of Europe, having its sources in the Swiss canton of Grisons, and flowing into the North sea by an extensive delta of five mouths in Holland, after a circuitous but general N. N. W. course of about 800 m. The Rhine is usually divided into three parts, the upper, middle, and lower, the first lying within and along part of the boundary line of Switzerland, the second between Basel and Cologne, and the third between Cologne and the sea. The river originates in the Lepontine Alps in three branches, the Vorder, Mittel, and Hinter Rhein, the first and most western of which is considered the principal source. It rises in lat. 46° 38' N., lon. 8° 48' E., in the small lake of Toma, on the E. side of a mountain of the St. Gothard group, 7,687 ft. above the sea, runs as a torrent for about 12 m., during which it descends nearly 4,000 ft., and is joined at Dissentis by the Mittel Rhein from the right. It then flows in a general E. by N. direction for about 36 m. to Reichenau, where it receives the Hinter Rhein, also from the right, and becomes about 180 ft. wide, and navigable for river boats.

Having continued the same course to Coire, it thence flows through a valley about 50 m. long and from 1 to 2 m. wide in a northerly direction to the lake of Constance, and for part of the distance forms the boundary line separating the principality of Liechtenstein and the Austrian district of Vorarlberg from Switzerland. After issuing from the lake at Constance it flows for a few miles in a westerly direction, till it enters the Untersee, which is about 30 ft. lower than the lake of Constance. It continues its course in the same direction to the falls of Schaffhausen, a little way below the town of that name, where the surface of the river is 1,280 ft. above the sea, and the falls vary from 60 to 75 ft. in height. Below these falls the general course is still westerly, but very tortuous; and the river flows between mountains for about 50 m. to Laufenburg, where the navigation is again interrupted by a cataract. The bed is here narrowed to about 50 ft., and boats ascend and descend by means of ropes after being unloaded. About 10 m. below Laufenburg there is a rapid of considerable length, which is exceedingly dangerous, though it does not stop navigation.

This is the last impediment to the navigation of the upper Rhine. Below this rapid the level of the river is 850 ft. above the sea, and it is only 50 ft. less at Basel. Above this point the Rhine receives numerous tributaries, the most important being the Aar, which, emptying about 12 m. above Laufenburg, brings the drainage of the greater part of Switzerland. From the lake of Constance to Basel the Rhine forms the boundary line between Baden and Switzerland. - Where the middle Rhine begins at Basel, the river has left the mountainous region, and changed its course to a northerly direction. It flows for about 200 m., to Mentz, through a valley from 30 to 50 m. wide, extending between the Black Forest and other mountains on the east, and the Vosges and the Hardt mountains on the west, forming the boundary line between Baden and Alsace, and Baden and Rhenish Bavaria, and passing through Hesse-Darmstadt. Between Basel and Strasburg, about 80 m., the fall of the river is 4 1/3 ft. per mile, and the current very rapid. The bed is wide and obstructed by numerous movable sand banks and small islands, which render the navigation intricate and dangerous. For the next 60 m., to Germersheim, the islands increase in size and are less liable to shift their position.

Gold is washed from the sand and gravel along this part of its course, but not in paying quantities. Below Germersheim islands are rare, and the river flows sluggishly in large bends to Mentz, where its surface is only about 250 ft. above the sea. Many of the isthmuses formed by these bends have been cut through of late years, so as to shorten its course. Between Strasburg and Mentz it is navigable for boats of about 100 tons burden, which descend with the current, but in going up are tracked chiefly by horses. Between Mentz and Cologne, about 120 m., the course of the river is first W., then N. N. W., and afterward mostly N. W. It first forms the boundary between Hesse-Darmstadt and the Prussian province of Hesse-Nassau, and then between the latter and the Prussian Rhine province, which it enters near Coblentz. This part of the river runs between two mountain regions, where in many places the hills come so close to the banks of the river that there is scarcely room for a road. The produce of the extensive vineyards in this neighborhood is known as Rhenish wines. There is a ledge of rocks at Bingen which prevents steamers and barges from passing during foggy weather or at night. The surface of the water at Cologne is 120 ft. above the sea.

During its middle course the Rhine receives many tributaries; but, with the. exception of the Moselle, those from the west are all short and not navigable. On the right or E. side the tributaries are much larger and more numerous, the most important being the Neckar, Main, Lahn, and Sieg. - The lower Rhine extends for about 300 m. from Cologne to its mouths, and flows through a low level country, with the hills of Sauerland near its E. bank between Cologne and Düsseldorf. From Cologne to Wesel its course is mostly N. N. W., though very tortuous. From Wesel to the frontiers of Holland it flows N. W. Below Cologne the Rhine is navigable for sea-going vessels, and the fall from thence to its mouth is only about 4 in. in a mile, and the current extremely sluggish. Shortly after entering Holland, near the village of Pannerden, the Rhine divides into two arms, the southern of which takes the name of Waal, the northern preserving that of Rhine. The Waal, which joins the Maas, is here 210 yards broad, while the Rhine is only 114 yards, and about two thirds of the volume of water runs into the former.

After the separation the Rhine flows N. N. W., and near Arnhem, 12 m. lower down, it again divides into the Yssel, which runs N. to the Zuyder Zee, and the Rhine, which flows W. At Wyck, about 30 m. lower down, the Rhine divides for the third time, into the Leck and Kromme Ryn (Crooked Rhine), the former of which is the larger. The Kromme Ryn runs N. W. to Utrecht, where the last division takes place, into the Vecht, which flows to the Zuyder Zee, and the Oude Ryn (Old Rhine), which continues westward past Leyden. The mouth of the Oude Ryn was formerly obstructed by dunes or sand hills, and the river did not reach the sea; but in 1807 a canal was cut through them, and it now communicates with the North sea at Katwyk, a few miles N. W. of Leyden. Before it begins to form the delta the lower Rhine is augmented by the Erft, Ruhr, and Lippe, all of which are navigable. The Yssel was originally a canal cut by Drusus to unite the Rhine with the river now called Oude Yssel (Old Yssel). The Leck, or middle branch of the Rhine, was also originally a canal made by the Roman general Corbulo; but in A. D. 839 its bed was so much enlarged by a flood that it became the main stream.

The delta of the Rhine is bounded N. by the Zuyder Zee, E. by the Yssel, S. by the Waal and Maas, and W. by the North sea; it comprehends the three Dutch provinces of North and South Holland and Utrecht, and about two thirds of Gelder-land, all of which country would be subject to inundations were it not protected by embankments. These embankments begin in the Prussian district of Düsseldorf, extend along the banks of the different arms of the Rhine to the sea, and are generally from 25 to 30 ft. above the lowest level of the river. - The basin of the Rhine is estimated at 80,000 sq. m., of which 13,000 belong to the upper, 40,000 to the middle, and 27,000 to the lower Rhine. The river is generally covered with ice for from six weeks to two months in winter; and when snow accumulates and a thaw suddenly sets in, the lowlands are liable to inundations that are sometimes attended with great loss of life and property. The different arms of the Rhine are united by numerous canals, and the river itself is connected by canals with the Saône and Rhône, the Scheldt, Maas, and Danube; and an extensive trade is carried on upon all these as well as the chief navigable tributaries, the Moselle, Main, Ruhr, and Neckar. The annual traffic is of great importance, and is regulated by treaties between the different states through which it runs, all of which lay toll duties on vessels and goods passing their boundaries. - The Rhine is celebrated for the picturesque beauty of the scenery in the upper and middle part of its course, and is annually visited by a multitude of tourists.

More than 1,000,000 passengers are conveyed up and down annually. Steam vessels ply between the principal towns on its banks. It is crossed at several points by pontoon bridges, and many of the principal places on either side are connected by railways. There is great discrepancy among ancient writers with regard to the number of mouths by which the waters of the Rhine formerly flowed into the sea. Some speak only of two; others say there were three; and Caesar says there were several branches.