Buoy

[3] To the north there are early medieval mentions of the French / Belgian River Maas being buoyed.

[4] The simple barrel was difficult to secure to the seabed, and so a conical tonne was developed.

They had a solid plug at the narrow end through which a mooring ring could be attached.

[7] In 1879 Julius Pintsch obtained a patent for the illumination of buoys by using a compressed gas.

This could be set to flash which ensured that buoys could be distinguished from ships' lights and from each other.