Basel and Mainz, the tributaries, though numerous, are mostly
short and unimportant. The Ill and the Nahe on the left and the
Neckar and the Main on the right are, however, notable exceptions.
Before joining the Rhine the Ill runs almost parallel with it and
at no great distance for upwards of 50 m. In the narrow part of
the valley, between Bingen and Cologne, the Rhine receives the
waters of the Lahn and the Sieg on the right, and those of the
Mosel, bringing with it the Saar, and the Ahr on the left. Still
lower down, but before the Dutch frontier is reached, come the
Ruhr and the Lippe on the right, and the Erft on the left. The
numerous arms into which the Rhine branches in Holland have
already been noticed.
Physical Geography.—The Rhine connects the highest Alps with the mud banks of Holland, and touches in its course the most varied geological periods; but the river valley itself is, geologically speaking, of comparatively recent formation. Rising amid the ancient gneiss rocks of the St Gotthard, the Rhine finds its way down to the Lake of Constance between layers of Triassic and Jurassic formation; and between that lake and Basel it penetrates the chalk barrier of the Jura. The upper Rhenish valley is evidently the bed of an ancient lake, the shores of which were formed by the gneiss and granite of the Black Forest on the one side and the granite and sandstone of the Vosges on the other. Within the valley all the alluvial deposits are recent. Between Bingen and Bonn the Rhine forces its way through a hilly and rocky district belonging to the Devonian formation. The contorted strata of slate and greywacke rock must have been formed at a period vastly anterior to that in which the lake of the upper valley managed to force an outlet through the enclosing barriers. Probably this section may be looked upon as the oldest portion of the river course proper, connecting the upper Rhenish lake with the primeval ocean at Bonn. In this district, too, as has already been remarked, is the finest scenery of the Rhine, a fact due in great part to the grotesque shapes of the quartzose rocks, left denuded of the less durable slate and sandstone. All the strata intersected by the Rhine between Bingen and Bonn contain fossils of the same classes. The deposits of the actual valley here, belonging to the Miocene group of the Tertiary system, are older than the deposits either farther up or farther down the river; but they are contemporaneous with the basalts of the Rhine, which at Coblenz and in the peaks of the Seven Mountains also contribute to the scenic charm of the river. The very extensive pumice deposits at Neuwied and the lava and other volcanic rocks belong to a more recent epoch. Below Bingen the formations belong almost entirely to the Post-Tertiary period. Numerous extinct volcanoes rise near Neuwied. In the flatter parts of the valley occur large beds of loam and rubble, sometimes in terraces parallel with, but several hundred feet above, the river, proving by their disposition and appearance that the valley has been formed by the action of water.
Navigation.—The Rhine has been one of the chief waterways of Europe from the earliest times; and, as its channel is not exposed to the danger of silting up like those of the Elbe and the Oder, it has always been comparatively easy to keep it open. The Romans exerted themselves to improve the lower navigation of the river, and appointed prefects of the Rhine to superintend the shipping and to exact the moderate dues imposed to keep the channel in repair. The Franks continued the same policy and retained a system of river-dues. Afterwards, as the banks became parcelled out among a host of petty princelings, each of whom arrogated the right of laying a tax on passing vessels, the imposts became so prejudicial as seriously to hamper the development of the shipping. Many of the riparian potentates derived the bulk of their revenue from this source, and it is calculated that in the 18th century the Rhine yielded a total revenue of £200,000, in spite of the comparatively insignificant amount of the shipping. The first proposal for a free Rhine was mooted by the French at the congress of Rastatt (1797-1799), but Holland, commanding the mouth of the river, placed every obstacle in the way of the suggestion. In 1831, on the separation of Holland and Belgium, the former had become more amenable to reason; and a system was agreed upon which practically gave free navigation to the vessels of the riverine states, while imposing a moderate tariff upon foreign ships. After the war of 1866, Prussia negotiated with Baden, Bavaria and Hesse-Darmstadt with a view to the removal of all tolls. It was not, however, till 1868 (see Die Rhein-Schiffahrts Akte vom 17ten Okt., 1868) that the last vestige of a toll disappeared and the river was thrown open without any restriction. The management of the channel and navigation is now vested in a central commission, meeting at Mannheim on the 1st of July in each year. The channel has been greatly improved and in many places made more direct since the beginning of the 19th century, large sums being annually spent in keeping it in order. Capacious river harbours have been formed at various points, twenty-nine of these being in Germany and eight in Holland. The position of the river is highly favourable for the development of its trade. It flows through the most populous regions of the continent of Europe, to discharge into one of the most frequented seas opposite Great Britain, and, besides serving as a natural outlet for Germany, Belgium and Holland, is connected with a great part of central and southern France by the Rhine-Rhone and the Rhine-Marne canals, and with the basin of the Danube by the Ludwigs-Canal.
The introduction of steam has greatly increased the shipping on the Rhine; and small steamers ply also on the Main, the Neckar, the Maas and the Mosel. The first Rhine steamer was launched in 1817; and now the river is regularly traversed by upwards of a hundred, from the small tug up to the passenger saloon-steamer. The steamboat traffic has especially encouraged the influx of tourists, and the number of passing travellers may now be reckoned as between one and two millions annually. The river is navigable without interruption from Basel to its mouth, a distance of 550 miles, of which 450 lie within Germany. Above Spires, however, the river craft are comparatively small, but lower down vessels of 500 and 600 tons burden find no difficulty in plying. Between Basel and Strassburg the depth of water is sometimes not more than 3 ft.; between Strassburg and Mainz it varies from 5 to 25 ft.; while below Mainz it is never less than 9 or 10 ft. The deepest point is opposite the Lorelei (Lurlei) Rock near St Goar, where it is 75 ft. in depth; at Düsseldorf the depth is about 50 ft.
London, Hamburg, Bremen and the chief Baltic ports as far as Riga and St Petersburg participate in the traffic on the Rhine. The boats which ply up and down the river itself, without venturing upon the open sea, are mostly craft of 100 to 200 tons, owned in the great majority of cases by their captains, men principally of German or Dutch nationality. This fleet is computed to number some 8500 craft, with an aggregate capacity of over 2 million tons, of which about one-tenth are steamships. The traffic at the chief German ports of the river aggregated 4,489,000 tons in 1870, but by 1900 this had grown to a total of 17,000,000 tons, thus distributed: Ruhrort, 6,512,000 tons; Duisburg, 3,000,000 tons; Cologne, 1,422,000 tons; and Mannheim, 6,021,000 tons. These are not the only ports on the river; a large trade is also done at Kehl, Maxau (for Karlsruhe), Ludwigshafen, Mainz, Bonn, Rotterdam and a host of smaller places. The amount of traffic which passed the town of Emmerich near the Dutch frontier, both ways, increased from an annual average of about 6 million tons in 1881-85 to over 21½ million tons in 1899. Notwithstanding the inherent difficulties of construction caused by the great variations in the level of the stream, amounting sometimes to 20 ft. or more, the chief ports of the Rhine are admirably constructed, and well equipped with modern contrivances for loading and unloading vessels. Boats carrying as much as 600 tons are often able to proceed as far up stream as Strassburg, and smaller craft get as far as Hüningen, a little above Basel. Large passenger boats ply regularly between Mainz and Düsseldorf, and sometimes extend their journeys as high up as Mannheim, and as far in the other direction as Rotterdam. The efforts of the river authorities are being directed to the deepening and improvement of the navigable channel from the sea to Strassburg, the low-water depths aimed at being 10 ft. from Rotterdam to the German frontier, and 10 ft. thence to Cologne; 8 ft. 3 in. from Cologne to St Goar, and 6 ft. 6 in. from St Goar to Mannheim. At present the Rhine in Holland has a depth of about 9 ft. and a width of 1200 to 1300 ft., though the Merwede branch exceeds this depth by 8 in. Altogether a sum approaching £2,500,000 was spent in Holland within the latter part of the 19th century on the improvement of the Rhine and its principal arteries. Above Mannheim the depth of the stream is always less than 5 ft., and generally varies between that figure and 4 ft. 6 in. The difficulty of ascending the rapids near Bingen is usually surmounted by the help of steam hauling machinery placed on the bank, though powerful tugs have also come into use for this purpose. The work of blasting out the rocks which at that spot projected in the bed of the river, begun in 1830, was continued down to the year 1887, so that now there are two navigable channels of sufficient depth for all vessels which ply up and down that part of the stream. One of the most interesting features of the Rhine navigation is afforded by the huge rafts of timber that are floated down the river. Single tree trunks sent down to the Rhine by the various tributaries are united into small rafts as they reach the main stream; and these again are fastened together to form one large raft about Andernach. Though not so large as formerly, these timber rafts are still sometimes 400 or 500 ft. in length, and are navigated by 200 to 400 men, who live in little huts on the raft, forming actual floating villages. On reaching Dort the rafts are broken up and sold, a single raft sometimes producing as much as £30,000. The voyage from Bingen to Dort takes from one to six weeks, and the huge unwieldy structures require to be navigated with great care. The commerce carried on by the river itself is supplemented by the numerous railways, which skirt its banks and converge to its principal towns. Before the introduction of railways there were no permanent bridges across the Rhine below Basel; but now trains cross it at about a dozen different points in Germany and Holland.
History.—Politically the Rhine has always played a great part. The whole valley seems to have been originally occupied by Celtic tribes, who have left traces of their presence on the contents of tombs and in the forms of names (Moguntiacum
