the City of Paris struck a mine but escaped with little damage. As the weeks passed losses became more serious, and statements made by a prisoner of war revealed that the enemy was discharging magnetic mines from submarines. This evidence appeared to be confirmed by a number of unexplained explosions rind sinkings off the .roast.

Hitler had boasted of his " se.cret weapon " and it seemed that this might be the magnetic mine. It was not, however, a new invention, for the Royal Navy had used magnetic mines

off the Belgian coast during the previous war, and, so far from its being a secret, an American citizen, Mr. Caesar Marshall, had been granted a British patent for such a device in 1918. Other inventors had experimented with mines of similar type, and the Mine Experimental Department of H.M.S. Vernon was well aware of their existence ; indeed, its own magnetic mines were; in an advanced state of development.

The   magnetic   mine   is   so   called,   not