Of these waterways of decided commercial importance.
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.
They are constructed not only as navigable waterways, but also to relieve the rivers from periodical overflow, and to drain the marshy districts.
The inland waterways include the 25 ft.
Other important waterways which have been authorized by the United States government and on which work was proceeding in 1910 are canals from the Rio Grande river to the Mississippi river at Donaldsonville, Louisiana; and "a navigable channel depth of 5 ft.