January 250
February 380
March 473
April 515
May 360
June 470
July 404
August 352
September 418
October 237
November 184
December 188

making the average per month in 1917 355 mines.

It will be noticed how rapidly the figures rose in the early part of the year, and how great was the diminution in the figures for the later months.  This decrease was due to the fact that the extension of anti-submarine measures was beginning to take effect, and the destruction of German submarines, and especially of submarine minelayers of the U.C. type, was becoming considerable.

The heavy work involved a great strain on the minesweeping service, and the greatest possible credit is due to the personnel of that service for the fine response made to the call for additional exertions and heavier risks.

At the same time the organizing work achieved at Headquarters by the minesweeping section of the Naval Staff should not be forgotten.  At the head of this section was Captain Lionel G. Preston, C.B.; he had succeeded to the post of Head of the Minesweeping Service early in 1917, after two and a half years of strenuous and most successful minesweeping work in the Grand Fleet flotillas, and he at once grappled with the task of dealing with the large number of mines then being laid by German submarines.

Instructions were issued to fit all patrol craft round the coast for minesweeping work in addition to their patrol duties, and they were used for sweeping as required.  Many drifters were also fitted for minesweeping in addition to the trawlers hitherto employed; and although there was some prejudice against these vessels on account of their slower speed, they proved to be of great assistance.  Every available small craft that could be fitted for the work was pressed into the service, including a considerable number of motor launches.

There was unfortunately great delay in the building of the “Hunt” class of minesweeper, which was the type ordered in 1916 and repeated in 1917, and in spite of very large additional orders for this class of vessel having been placed early in 1917 (a total of 100 extra vessels being ordered), the number completed during that year was only sixteen, together with a single paddle sweeper.  Consequently we were dependent for the largely increased work on improvised craft, and the very greatest credit is due to all who were concerned in this arduous and dangerous duty that the waters were kept comparatively clear of mines, and that our losses from this cause were so small when the immense number of mines swept up is considered.

Fortunately the enemy lost very heavily in submarines of the U.C., or minelaying type, largely because they were working of necessity in waters near our coast, so that our anti-submarine measures had a better chance, since they were easier to locate and destroy than submarines working farther afield.  By the commencement of 1918 the average number of mines swept up monthly showed a very remarkable decrease, the average for the first two months of that year being only 159 per month, eloquent testimony to the efficiency of the anti-submarine measures in operation during 1917.  I have no information as to the figures for the remaining months of 1918.