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Count Dohna and His SeaGull ©

Sea Mines

The SeaGull set moored contact mines, each weighting 2,200 pounds. This was much larger than the mines sown later in the war when most German mines were less than half that weight. Contact mines detonate when the moored mine comes in contact with anything.
Moored mines connect to an anchor by a cable. Should the cable separate the mine becomes inactive and will not detonate if contact is made. This prevents the mines drifting from the area where sown and becoming a haphazard menace to navigation. Mines are moored at a depth so that the mines are not visible on the surface at low tide. The mines set by SeaGull were moored to a greater depth so that only deep draught ships would encounter them. Mines are sown at predetermined distances so that an exploding mine does not detonate surrounding mines.
The strategic purpose of mining is to create an area that cannot be used by the enemy and requires the avoidance of the area. It is not expected that a significant number of ships will be damaged or sunk.
SeaGull set the "Whiten Bank" minefields off the northern coast of Scotland. These fields were set in close to shore. Ships passing the area were forced to sail further from shore to avoid the minefields. In this area, ships tried to keep close to shore where the waters are shallow and submarines could not safely operate. Because of the mines the ships sailed in deeper waters and where therefor more prone to submarine activity.


Throughout the war, the British method for mine searching and clearance consisted of a single .22-inch serrated wire towed between two vessels steaming abreast. The sweep is to cut the mooring cable of the mine, which comes to the surface where it is detonated by rifle or machinegun fire. Frequently the sweep explodes the mine which parts the sweep wire. A delay is caused while a new wire is passed between the vessels.
Minesweeping was dangerous duty. The 2,200 pound mines set by SeaGull off the coast of Northern Scotland were particularly deadly. This particular area, over 1,000 square miles, was declared unusable and was finally cleared years later, after the war ended.

Anti-sweeping Techniques

Anti-sweeping measures were used to complicate the process of clearing mined areas. A short chain with a hook at the end was suspended from the bottom of some mines. When the sweep wire cuts the anchor cable of a mine, the hook catches the sweep wire. The mine is then connected to the sweep wire. If the mine reaches the surface and detonated by riffle-fire the sweep wire is parted. Or if the mine is not detected while sweeping it presents a true hazard when the sweep wire is hauled aboard the ship at the completion of the sweep.

Bayo, Spanish steamer, mined and sunk on January 13, 1916.
Belgica, Spanish steamer, mined and sunk on January 15, 1916.
Bonheur, Norwegian steamer, mined and sunk on January 7, 1916.
Duckbridge, British collier mined and sunk on February 22, 1916.
HMS King Edward VII, British warship mined and sunk on January 6, 1916.
Wilston, British collier mined on February 15, 1916.

, by Charles Beresford.
THE HIDDEN MENACE, by Maurice Griffiths.
THE GRAND FLEET 1914-1916, by Admiral Viscount Jellicoe of Scapa, Doran, 1919.

Last Revision: March 4, 2007.
© Copyright, 2007.
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