On May 6th the mine-layer _Orvieto_ and eight destroyers left Scapa to carry out a mine-laying operation in the Heligoland Bight. The force ran into a dense fog, and a collision occurred between the destroyers _Comet_ and _Nemesis_, the latter being seriously damaged. The force was directed to return and left Scapa again on the 8th, carrying out the operation successfully during the night of the 10th–11th; it returned on the 12th. The light cruisers _Phaeton_ and _Royalist_ left Scapa on May 12th for a position north of the Shetlands, in order to intercept a neutral steamer reported to have left Bremerhaven on May 11th with wireless installations on board. The C Patrol of the 10th Cruiser Squadron was also moved to a position to intercept this vessel, and the light cruiser _Sappho_ and armed boarding steamer _Amsterdam_ were placed on the western side of the Fair Island Channel. The force returned on the 14th, the report proving to be incorrect. The whole Grand Fleet carried out a sweep of the central part of the North Sea between May 17th and 19th, the forces from Scapa, Cromarty and Rosyth meeting at a rendezvous in Lat. 57.10 N., Long. 0.0 at 7 A.M. on the 8th, and sweeping to the south-eastward at a speed of 16 knots until the afternoon, with the Battle Cruiser Fleet some thirty to fifty miles ahead of the Battle Fleet. The Fleet returned to its bases on the 19th, not having sighted any hostile vessels. Battle tactics were exercised during the passage north. On May 21st the Fleet mine-sweepers, which had been sent to Aberdeen beforehand in readiness, left with an escort of two light cruisers to examine the mine-field reported to have been laid in the centre of the southern portion of the North Sea. Two of the sweepers collided in a fog on leaving Aberdeen, and another went ashore; the remainder proceeded and located the north-east corner of the mine-field on the 22nd and 23rd; they returned to Aberdeen on the 24th, after examining _en route_ a position in which it was reported that paraffin barrels were moored. These were destroyed. It was thought that they might be intended for German submarines. Whilst the Fleet sweepers located the north-east corner of the mine-field, paddle sweepers, under the escort of two light cruisers from Harwich, located the south-west corner. The search was subsequently continued under the same conditions, and the limits of the mine-field, which covered a large area south of Lat. 56 N. and east of Long. 2.30 E., were determined. The enemy made no attempt to interfere with the sweeping operations, if indeed he was aware of them.