THE AUTHOR, Sydney David Waters, is a New Zealand journalist who has
specialised in naval and merchant shipping affairs. He is the author of two
histories of the New Zealand Shipping Company, Clipper Ship to Motor-liner
and Ordeal by Sea, and of Pamir: the story of a Sailing Ship. He served as a gunner
in the ist NZEF during the First World War.

– 33 –

Moored CONTACT mine (left) is the type laid by the German raider Orion.
Anchored at pre-determined depth it is fired by contact with projecting horns.
Antenna mine is detonated by contact with antenna.

FREE mines drift, creep, or float, according to type. Oscillating mines are fitted
with a hydrostatic switch which is operated by water pressure as the mine rises
or sinks.

GROUND mines are detonated by the action of the magnetic field, by the noise
of a ship, or by the displacement of water. The German raider Adjutant laid
magnetic ground mines close to the entrances of Wellington and Lyttelton
harbours.