In the 14th century and afterwards extended to more than 650 yds., has been greatly improved since 1875 by dredging and a further addition to the mole of 136 yds.
By dredging and the construction of jetties the Federal government has since 1885 greatly improved the channel at the mouth of the river.
A considerable number of men are engaged in the various states on alluvial fields, in hydraulic sluicing, and dredging is now adopted for the winning of gold in river deposits.
The large boats, dredging from March to October, collect from 650 to 850 lb of coral, and the small, working throughout the year, collect from 390 to Soo lb.
Systematic dredging on a large scale was at one time carried on in the Kurisches Haff by Messrs Stantien and Becker, the great amber merchants of Konigsberg.
Sand bars keep filling up the mouths of these channels, necessitating frequent dredging and extension of the breakwaters, work undertaken by the Federal government, which also maintains a most comprehensive and completeystem of aids to navigation, including lighthouses and lightships, fog alarms, gas and other buoys, life-saving, storm signal and weather report stations.
Tondern was in early days a seaport, but since the reclamation of the marshes and the dredging of the Widane navigation has ceased, and vessels load and unload at Hoyer, with which the place has direct railway communication.
Over the sill at high water of spring tides; the construction of new jetties at the entrance to the tidal basin and at the north wall; the establishment of a coal wharf with hydraulic appliances; a torpedo range in the harbour; the erection of various buildings such as torpedo and gun-mounting stores, electrical shops and numerous subsidiary works; and extensive dredging of the harbour to increase the berthing accommodation for the fleet.
The line progressed rapidly, and by the end of 1921 only the dredging of the Zambezi remained to be accomplished.
In 1908 the breakwaters and the greater part of the dredging had been completed, and the entrance channel, with a minimum depth of 242 ft., permitted the admission of large steamers.