MAGNETIC MINES

Waikato Times, Volume 125, Issue 20995, 23 December 1939, Page 11

MAGNETIC MINES

ATTRACTION THEORY DERIDED BY EXPERTS (Times Air Mail Service ) LONDON, Nov. 21 The theory expressed in some quarters that the sinkings of the Simon Bolivar and other vessels were caused by a new “magnetic” mine, attracted upwards from the bottom of the sea by the steel hull of a ship, was laughted at by naval experts yesterday. Though it is possible to detonate mines by a variety of methods, and it is conceivable that a firing device could be used, in which a magnetised plunger or trigger operated, it is doubtful if it would be much more efficient than the contact firing devices now common. The strength of a ship’s magnetic field would not be great enough to operate it at a distance of more than a few yards from the ship’s hull. It is likely (writes the naval correspondent of the News Chronicle) that, as in the last war, the mines are moored with a temporary connection which is, in due course, severed by the chemical action of sea-water and the mine brought to the surface. No Miniatures It is probable that the mines are laid by U-boats. Almost any of those in service, or on the point of completition at the beginning of September may have been so equipped. There were 71 of these, of which 32 were of the small 250-ton type, suitable only for Baltic or North Sea operations. More than 20 U-boats have unquestionably been destroyed, leaving fewer than 50 in commission, soma of which must have been badly damaged. It is questionable if the rate of construction reached during the last war can be exceeded, even if reached. A rumour that Germany is building miniature submarines with a crew of one or two men should not be taken too seriously. Such vessels could be of little value save for harbour defence.