Inland Waterways as Carriers of Commerce.—Inland waterways, including rivers, canals, and lakes, are especially important as carriers of commerce in backward countries like China, Siberia, and northern Brazil, which possess large rivers, but have not a highly developed railway system. They are also important in advanced countries like Holland and Germany, where numerous rivers flow through densely populated plains. Nevertheless, in view of the cheapness of water transportation, the use of inland waterways is by no means so great as would be expected. This is because a good inland waterway must be favorable in each of the following respects, all of which are rarely satisfactory in a single body of water: (1) depth and breadth; (2) length; (3) character of the course; (4) current; (5) seasonal changes; (6) hinterland; and (7) direction.
(1) Depth and Breadth.—These two qualities are closely connected and both depend largely on volume. If a river comes from a region of heavy rainfall it is likely to have great volume and hence to be deep enough and broad enough for important traffic. The Amazon is such a river. For a distance of 2300 miles its vast volume causes it to average 120 feet deep and to have a width of more than a mile and often five or six. So vast is the river that while a ship is still beyond sight of land the sailors sometimes let down buckets and draw up fresh water from what seems to be the ocean, but is really the enor mously wide mouth of the river. Cases have actually been known where sailors have died of thirst when adrift on the fresh water at the mouth of the Amazon.
The Rio Grande illustrates the opposite condition. Although it is half as long as the Amazon, it is practically unused for navigation. It comes from a region of such sparse rainfall that it has little volume and hence very slight depth. Even at its mouth it is shallow, and higher up it sometimes is dry. On almost all rivers the presence of sandbars at the mouth and of other shallow places higher up is one of the chief hindrances to navigation.
(2) Navigable Length.— The length of the navigable stretches on a river is of the first importance. The Yangtse, for example, is navigable for 1000 miles in one continuous stretch from its mouth far into the heart of China. This makes it of great value for com merce. The Orange River, on the contrary, although it has an actual length of 1300 miles, is of no value for navigation, because the stretches where boats can ply extend only a few score miles. It would never pay to ship goods fifty miles by boat, then thirty by rail, again one hundred by boat, once more by rail, and so on. The reason is that trans-shipment is very expensive. With some kinds of freight it actually costs more to load a ton onto a steamer and take it off again than to carry it all the way from New York to Liverpool, and even with kinds that can be loaded inexpensively a single loading costs as much as scores of miles of actual transportation. Hence no
waterway is of much use for commerce unless its navigable reaches are long and uninterrupted.
(3) Character of Course.—Straight rivers like the Amazon, Hudson, and St. Lawrence are far the best for navigation. On rivers with winding courses not only are distances much increased, but the channel is almost sure to wind still more, so that little speed can be made, and there is danger of running aground. On the Mississippi, which has an extremely winding course, some of the meanders or bends are so extreme that after flowing ten or fifteen miles around a horse-shoe curve the stream comes back to within a few hundred yards of its earlier position.
(4) Current.—The more gentle the current of a river the better it is for navigation. The great Volga River, even at its source, is only 665 feet above sea level, while 1500 miles from its mouth it is only 190 feet above the level of the ocean and 280 above the Caspian. Hence throughout most of its course the current is so gentle that ships are little impeded and locks and dams are unnecessary. Contrast the Volga with the Brahmaputra, which rises 15,500 feet above the sea, and flows so swiftly over rapids and falls that along much of its course no one has ever used a boat. The Zambesi is another great rive along which numerous rapids, in addition to the great Victoria Fall. divide the navigable water into sections too short to be of much use. The other great African rivers suffer the same disadvan'fige. Even the Nile, which has 2900 miles of uninterrupted at high water, is at most seasons broken into many sectiontOwapids, or cataracts, as they are called. ' (5) Seasonal Changes.—Practically every river is ,,,,oject to strong seasonal changes. Floods and droughts are more or less universal, while freezing is common. The rivers most free from floods coin from great lakes, as in the case of the St. Lawrence, or receive an abundant supply of rain at all seasons, as is the case with the two greatest equatorial rivers, the Amazon and Congo. The rivers of Siberia have the disadvantage not only of floods, but of ice. In the winter the Amur, for example, is frozen for six months; then when the ice breaks up, great floods occur and would wash away not only the shipping, but the floating docks, which are the only kind possible, if these were not all safely moored in harbors of refuge. Later, however, in May and June, the floods make navigation easy, since the shallows are deep and the rapids smooth. Finally, in the fall before the river freezes up, it falls so low that ships are greatly ham pered by the danger of running aground.