The _Broke_ and 12 destroyers left on the 27th to search for a submarine reported to have been sighted to the eastward of the Pentland Firth, and returned on the 28th, not having seen her; but on the 27th Trawler Unit No. 42, working from Peterhead, reported having engaged and sunk a submarine at 12.45 P.M. in Lat. 57.10 N., Long. 1.20 E., thus adding one more success to the record of this patrol. On the 30th Fleet-sweeper _Gentian_ was missed, in a position about 40 miles due east of the Pentland Firth, by a torpedo fired evidently by the submarine that had been hunted on the 28th. A half flotilla and sea-planes were sent out to search, and a submarine was sighted at 3.45 P.M. near the position given, but she dived and got clear away. The movements of the Fleet between the time of leaving and returning to the bases in connection with the Battle of Jutland are given in Chapter XI., but some mention may be made of an incident which occurred on the night of May 31st. A report was received at Scapa that an enemy raider might be attempting to escape into the Atlantic. The Vice-Admiral of the 10th Cruiser Squadron was directed to assume a patrol north of the Shetlands in accordance with a plan which had been pre-arranged to meet such a case. On June 3rd, after the return of the Fleet to its bases, light cruisers were sent out to patrol to the north-westward of the Orkneys, and the 10th Cruiser Squadron was then directed to fall back to a position farther west to form a second patrol line. Nothing came of the matter. During the month of May the weekly average results of the 10th Cruiser Squadron showed: Number of vessels intercepted, 55, besides 17 trawlers; number sent in, 18; number of ships on patrol, 11; number absent at ports or _en route_ to or from patrol, 9; number on special service, 2. A good deal of fog and mist was experienced during the month, the worst periods being from the 17th to the 20th, 24th, 26th, and the 28th to 30th. During the month of May the firing exercises in the Pentland Firth continued, as did the usual exchange of bases between squadrons. During the months of March, April and May, a flotilla of submarines had been gradually organised as a unit of the Grand Fleet. It was named the 11th Submarine Flotilla, was based on Blyth, with the _Titania_ as parent ship and the _Talisman_ and _Trident_ as attendant destroyers. Separate spheres of activity for the Grand Fleet submarine flotillas and for the submarine flotillas based on Harwich and Yarmouth were also arranged, the dividing line running from a position a little to the southward of the Horn Reef to Flamborough Head. The line was subsequently slightly altered once or twice as the strength of the Grand Fleet submarine flotillas increased, but the general principle was that the Grand Fleet submarines worked to the northward of such a line and the remaining submarines to the southward.