MAGNETIC MINES

Wairarapa Times-Age, 29 November 1939, Page 3

MAGNETIC MINES

NAZI “SECRET WEAPON.” The Germans are reported to be using “magnetic mines ’ in their new campaign at sea. There remains little doubt in most people’s minds that the “secret weapon" with which the Allies were threatened recently has now been revealed as mine warfare, but it can also be accepted that the threat included also, or possibly referred only to, any advantage which the magnetic attribute confers. It cannot have been any secret that the Germans would use mines, for they are specialists in their use; or that they would not bother about rules and conventions, since they are also specialists in not bothering. But it may have been a secret that they had developed the magnetic type. A submarine mine is a tank containing a quantity of explosive—as much as half a ton. It may sit on the bottom, or be anchored at a chosen depth, or allowed to float free. It must have some means by which it is exploded; and this must be operated either by contact with the object it blows up or by some other means. The contact mine is of a single international type. It is fitted with a number of projecting “horns" which, if bent or broken by striking a ship's side, release the firing gear inside the mine, with sudden and spectacular effect. Such mines are not selective: they explode, whatever hits them. Non-contact mines are fired either by electrical means under human control when a chosen target is close enough—a system of very limited usefulness —or by some mechanism, not under control, sensitive enough to detect the presence of a target near enough to be damaged. It is to this class that the magnetic mine belongs.