in the Heligoland off our own coasts Bight.

to catch submarines.
1915 4,498 983 1916 1,679 2,573 First quarter of 1917 4,865 ) Second quarter of 1917 6,386 ) 3,843 Third quarter of 1917 3,510 ) In the Straits of Dover, Thames Estuary and off the Belgian coast we laid 2,664 mines in 1914, 6,337 in 1915, 9,685 in 1916, and 4,669 in the first three quarters of 1917.
These last mines were laid as fast as the alterations, made with a view to increasing their efficiency, could be carried out.
During the early part of the year 1917 the new pattern of mine, known as the "H" Type, evolved in 1916, had been tried, and although not perfectly satisfactory at the first trials, the success was sufficient to warrant the placing of orders for 100,000 mines and in making arrangements for the quickest possible manufacture.

This was done by the Director of Torpedoes and Mines, Rear-Admiral the Hon.

Edward Fitzherbert, under the direction of the then Fourth Sea Lord, Rear-Admiral Lionel Halsey.
Deliveries commenced in the summer of 1917, but by the end of September only a little over 1,500 were ready for laying.

Some 500 of these were laid in September in the Heligoland Bight and were immediately successful against enemy submarines.