The mine problem in the North Sea. The mine layer at work, showing the way in which the mine is held below the water and how it is exploded by a passing ship. The operation of the twin mine -- pressure on the cable explodes the charge which blows up the ship. A floating mine, noticeable from the decks of passing steamers. Mine sweeping and exploding -- an operation of the greatest danger. Including a map showing the disposition of German cruisers and gunboats in the Norwegian fjords just before the outbreak of war.