The first difficulty lay in the fact that we did not possess a thoroughly satisfactory mine. A percentage only of our mines exploded when hit by a submarine, and they failed sometimes to take up their intended depth when laid, betraying their presence by appearing on the surface. Energetic measures were adopted to overcome this latter defect, but it took time and but few mines were available for laying in the early months of 1917. The result of our minelaying efforts is shown in the following table: Mines laid Deep mines laid Year. 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. More were laid in the Bight during October, November and December, and the remainder, as they were produced, were prepared for laying in the new minefield in the Straits of Dover. _In the fourth quarter of the year a total of 10,389 mines was laid in the Heligoland Bight and in the Straits of Dover._ During this last quarter delivery of "H" pattern mines was as follows: In October 2,350, November 5,300, December 4,800; total 12,450. So that it will be seen that the mines were laid as fast as delivery was made. The great increase in projected minelaying operations during the year 1917 made it necessary also to add considerably to the number of minelaying vessels.