16

ON THE OUTBREAK OF WAR in 1914, Germany immediately showed that she relied on the mine as a weapon of offence. Within a few hours of the declaration of hostilities a British trawler sighted the Konigin Luise, a small converted mail-steamer, laying mines thirty miles off the coast of Suffolk. British destroyers sank her, but the following morning the cruiser Amphion struck one of her mines and went down with the loss of 151 lives.

The regular minesweeping force then consisted of no more than six old torpedo-gunboats. But the Reserve was being mobilized, and by 8th August, 1914, fishing trawlers were at sea, sweeping for mines, manned by their ordinary crews of fishermen. Within a fortnight another hundred trawlers had been requisitioned. So eager was the fishermen's response that in eleven days the whole force was manned and fitted out at Lowestoft.

By the end of August a clear channel had been swept and buoyed, inshore of the minefield laid by the Konigin Luise. This was the beginning of the War Channel which eventually extended from Dover to the Firth of Forth, a distance of 540 miles, and was swept daily. The forces employed on this service were based on the Nore, Harwich, Lowestoft, the Humber, the Tyne and Granton in the Firth of Forth.

The mines with which the sweepers had to contend were globular or pear-shaped, some three feet in diameter, containing about 350 lbs. of guncotton, trinitrotoluene (T.N.T.) or amatol. This explosive, with the firing batteries, occupied about half the space available, the remainder being used as an air chamber to give buoyancy to the mine. On the upper surface were five or more leaden horns five inches long, each holding a glass tube containing a chemical mixture. Contact with a ship fractured the horn and smashed the glass tube ; the released liquid then energized the battery, which fired the detonator. On one occasion a whale was killed by hitting the horn of a mine.

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When the laying vessel dropped the mine, both the mine and the sinker to which it was attached went straight to the bottom. After a short interval, which allowed the ship to steam clear, the mine was automatically released and rose under its own buoyancy, unreeling its mooring wire, while the sinker remained below. The depth of the mine beneath the surface was regulated by a device called the hydrostat, which gripped the mooring wire when the mine had reached the required height.

The trawler's task was to cut this mooring-wire so that the mine would either detonate in the wire sweep or rise to the surface, when