lowlands for the combined purpose of irrigation, drainage, and navigation.  The great canal system of China, constructed in the seventh century primarily to facilitate Inland intercourse between the northern and central sections of the Empire, extends from the sea at Hangchow 700 miles northward through the coastal alluvium of the Yangtze Kiang, Hoang-ho and Pie-ho to Tientsin, the port of Peking.  Only the canal system of the center, important both for the irrigation of the fertile but porous loess and for the transportation of crops, is still in repair.  Here the meshes of the canal network are little more than half a mile wide; farmers dig canals to their barns and bring in their produce in barges instead of hay wagons.[669] Holland, where the ancient Romans constructed channels in the Rhine delta and where the debouchment courses of the Rhine, Meuse and Scheldt present a labyrinth of waterways, has to-day 1903 miles (3069 kilometers) of canals, which together with the navigable rivers, have been important geographic factors in the historical preeminence of Dutch foreign commerce.  So on the lower Mississippi, in the greatest alluvial area of the United States, the government has expended large sums for the improvement of the passes and bayous of the river.  The Barataria, Atchafalaya, Terrebonne, Black, Teche and Lafourche bayous have been rendered navigable, and New Orleans has been given canal outlets to the sea through Lakes Salvador, Pontchartrain and Borgne.

[Sidenote:  Watershed canals.]

As the dividing channels of the lower course point to the feasibility of amplifying the connection with the ocean highway, so the spreading branches of a river’s source, which approach other head waters on a low divide, suggest the extension of inland navigation by the union of two such drainage systems through canals.  Where the rivers of a country radiate from a relatively low central watershed, as from the Central Plateau of France and the Valdai Hills of Russia, nature offers conditions for extensive linking of inland waterways.  Hence we find a continuous passway through Russia from the Caspian Sea to the Baltic by the canal uniting the Volga and Neva rivers; another from the Black Sea up the Dnieper, which by canals finds three different outlets to the Baltic through the Vistula, Niemen and Duna.[670] The Northern Dwina, linked, by canals, with the Neva through Lakes Onega and Ladoga, unites the White Sea with the Baltic.[671] Sully, the great minister of Henry IV. of France, saw that the relief of the country would permit the linking of the Loire, Seine, Meuse, Saone and Rhine, and the Mediterranean with the Garonne.  All his plans were carried out by his successors, but he himself, at the end of the sixteenth century, began the construction of the Briare Canal between the Loire near Orleans and the Seine at Fontainebleau.[672] Similarly in the eastern half of the United States, the long, low watershed separating the drainage basin of the St.