ever, were too slow for emergencies, and ordinary excursion paddle-steamers of light draught and good sweep were intro- duced with very successful results. A special design of sloop the “Flower” class of 1,200 tons, 250 ft. long, u ft. draught and 16 knots was laid down in large numbers, but these were not ready till April 1915. The loss of the “Audacious” off Tory I. (Ireland, N.) on Oct. 27 still further emphasized the necessity of a large and efficient minesweeping service. The minefield laid by the German s.s. “Berlin” consisted of some 200 mines running approximately N.E.-S. W. north of Tory Island. It was not definitely located till Dec. 20, and, though 43 mines had been swept up and 70 drifted ashore by the end of April, was not cleared till July 1915. It must be remembered that the loss of a ship or the discovery of a mine merely served to indicate the proximity of a minefield. Before its extent could be defined and the clearance completed a number of exploratory sweeps were required which were often delayed by bad weather. The German mines laid during 1914 were laid by surface craft in the following areas:—
|Aug. 5||“Konigin Luise”||Southwold||108|
|Oct. 26||“Berlin”||Tory I. (Ireland)||200|
|Nov. 3||“Kolberg”||Smith's Knoll||130|
They accounted for 42 merchant vessels or approximately one vessel for 24 mines. The measures taken to meet the danger consisted in the establishment of a war channel and the preliminary steps for a great expansion of the minesweeping service.
Minelaying played an important part in the German raids on the east coast, and the raid on Dec. 16 1914 was intended to cover a minelaying operation by the “Kolberg,” in which she laid 100 mines off Scarborough. Two of these mines were found by gunboats on Dec. 19, and half an hour later a Grimsby trawler minesweeping unit brought 18 to the surface simultaneously. Two of its trawlers struck mines and the field was not finally cleared till April 1915, 69 mines being accounted for out of 100 laid, with heavy losses to shipping, including 7 British and 7 neutral steamers, 2 trawlers, 4 minesweepers and an armed yacht.
By April 1915 the minesweeping forces had increased con- siderably and were distributed as follows: Grand Fleet, 6 gunboats, i sloop and 9 trawlers; Scotland, east, 47 trawlers; Humber, 6 paddlers, 30 trawlers; Lowestoft (war channel), 47 trawlers; Harwich and More, 33; Dover, 12; South Coast, 24; West Coast, 4; Clyde, 6 paddlers (fitting out). The principal minefields laid by German surface craft in 1915 were:—
|Spring 1915||Eastern Dogger Bank||480|
|April 4||Humber approach||360|
|(Swarte Bank and Indefatigable minefields)|
|Aug. 7-8||Moray Firth by “Meteor”||380|
|Jan. I 1916||Whiten Bank (west of Orkneys) by “Moewe”||252|
The Eastern Dogger Bank minefield was large but not a single British vessel of any size was lost in it. Sixty-nine mines were swept up there and the swell of the winter sea probably completed the task of clearance.
The fields off the Humber were responsible for the loss of 4 British, and 5 neutral steamers and 3 minesweepers, but the field was defined by May 1915; 127 mines were swept up that month and by the middle of July it was clear. The fields laid by the “Meteor” in Aug. 1915 and by the “Moewe” on Jan. 1 1916 were aimed directly at the Grand Fleet. The “Meteor” made the Scottish coast at dusk on Aug. 7 and, starting from a position about 22 m. N. of Kinnaird Head, laid 380 mines in the approach to the Moray Firth during the night. The first notification of them came from a Cromarty trawler minesweeper making a routine sweep on the morning of Aug. 8. The destroyer “Lynx” was lost the same day and the sloop “Lilac” had her bows blown off. After clearing a 10-m. channel along each shore and removing 222 mines, the rest of the field was left unswept as a protection against similar attacks. In the final mine clearance in 1918 only four mines were found in it.
The German minefields on the east coast gave rise to the erroneous idea that they were associated with a prospective landing operation. An equally erroneous idea that mines were laid by neutral trawlers obtained so firm a hold in the Grand Fleet that it led the commander-in-chief to ask for the exclusion of all neutral trawlers from British ports.
In the Mediterranean minesweeping played an important part in the attempt to force the Dardanelles. The problem was the same as that which confronted the Germans at Osel in the Baltic in 1917. The task was one of peculiar difficulty, for it meant sweeping under the fire of batteries, and the strong current reduced the speed of trawlers with sweeps out to less than 3 knots. It was a task which required high-speed sweepers and a highly trained personnel, and even with their agency its feasibility may be doubted. The technical difficulties of the task were greatly underestimated. It was regarded as a simple piece of work which any vessel fitted with a sweep could perform, and it was attempted with a motley collection of slow trawlers, assisted by a parcel of destroyers fitted with sweeps for the first time. The sweep principally used at this time and throughout the war was the “A” sweep, consisting of a single 2j-in. wire towed between two ships steaming 500 yd. apart, with its depth regulated by a water-kite 12 ft. long and weighing a ton. The end of the wire had to be passed from one vessel to the other and to do this rapidly under fire required an exceptional combination of training, skill and courage. In the case of fast sweepers, the momentum of the wire was sufficient to cut the mooring of the mine, but slow sweepers in the early years of the war had to take their sweeps into shallow water where the mines could be seen and sunk. This made sweeping slow work, and it also meant that the “A” sweep was really only effective by day; so that sweeping a minefield under heavy fire was almost impracticable.
The year 1915 saw an important development in the use of submarines for minelaying by the Germans. The Flanders Flotilla were the first workers in this field and their mines were first discovered off the S. Foreland on June 2 1915. These were laid by small boats termed UC boats, equipped with 12 cylindrical mines with charges of 350 Ib. of T.N.T., carried in vertical shoots. The mine dropped with its sinker to the bottom and was released from the sinker by a “dashpot” arrangement about half an hour after reaching the bottom, giving the submarine time to get clear. The mooring- wire coiled into the sinker was drawn off by the mine as it rose, and when the proper depth was reached it was gripped by a strong spring clamp released by a hydrostatic valve. Submarine minelaying threw a heavy strain on the minesweeping forces at Harwich, Dover and the Nore, which were the areas principally affected at first, and the continuous location of small groups of mines gave rise to an incessant stream of orders for the diversion or stoppage of traffic which greatly hampered coastal navigation.
The Germans report having laid 648 mines between Grimsby and Dover by submarines in 1915, of which 150 were laid in the Dover area (not including the Belgian and French coasts), 180 off the Nore, 306 in the Lowestoft area and 1 2 off Grimsby. The number of mines swept up in this area was approximately 500, and the losses in the last six months of the year showed a serious increase, comprising 3 destroyers, 5 supply ships, one hospital ship, 2 Trinity House vessels, 34 British steamers, 24 neutrals, 10 fishing boats, 15 minesweepers (3 paddlers, 9 trawlers) a total of 94 vessels. In June 1915 the Germans had extended their minelaying to Archangel, and a unit of 6 trawlers had to be despatched there; the unit destroyed over 150 mines by October, with the loss of H.M.S. “Arlanza,” one trawler, 6 British steamers, one Russian and 2 neutrals.
The “Actaeon” sweep, called after the parent ship of the Sheerness torpedo school, came into use at this time. It was a single-ship sweep, consisting of a light wire, a small kite, a depth float and an explosive grapnel, and was towed from each quarter of a minesweeper. On meeting a mine, the explosive grapnel parted its mooring; the sweep proved particularly useful in locating new fields, and had the advantage over the “A” sweep that it could be used by night.