Dec. 7, 1939
The secret of Germany's mystery mine, which has caused such havoc to British shipping in recent weeks, today stands disclosed. . . . The British have succeeded in salvaging three of the new German mines.
The salvage operation - a most delicate task in view of the sensitive character of the new mines - preserved them intact. It has permitted naval experts to examine them in detail.
Here is how they work:
The mystery mines have no buoyancy. They do not have to float. That permits them to carry a great weight of explosive.
The shape of the mine, and the way in which its weight is distributed, is such that it comes to rest upon the bottom of the sea with its firing mechanism uppermost.
The actuating device is a short, soft iron bar, wound with fine wire. It is this which is affected by the magnetic field created when a steel ship passes overhead.
The Monitor is looking back at the events of World War II.