On December 20th a report was received that the submarine obstruction in Hoxa Sound had been found to be pierced; this led to steam being raised by all ships at Scapa, and the usual search by small craft was ordered; boats were also sent to explode charges on the bottom in the vicinity of the damaged portion of the submarine obstruction, where it was thought a submarine might have been entangled. Another alarm took place later, due to some trawlers inside Scapa Flow mistaking the concussion due to the explosion of these charges for torpedoes and firing warning signals in consequence. The precautions were kept in force until after daylight on the 21st. On that date Vice-Admiral Sir Cecil Burney arrived at Scapa in the _Marlborough_ and assumed command of the 1st Battle Squadron, Sir Lewis Bayly taking over the command of the Channel Fleet. On the 21st the 1st Battle Squadron and 1st Light Cruiser Squadron left Cromarty for Rosyth in obedience to directions from the Admiralty that the battle cruisers and light cruisers were to be based on the latter port. This change was one result of the Scarborough raid. The mine-sweeping gunboats rejoined the Grand Fleet on this date. On December 23rd the 2nd and 4th Battle Squadrons, with the _Iron Duke_, proceeded to sea to the westward of the Orkneys, and carried out target practice at the Sulis-Ker Rock, north of the Hebrides, on the 24th, passed through the Pentland Firth at 6 P.M. on that date, and proceeded into the North Sea for a sweep into southern waters. During daylight of the 25th the 1st Battle Squadron, the 2nd Flotilla and the 6th Cruiser Squadron from Scapa, the 3rd Battle Squadron, the 3rd Cruiser Squadron, the 1st Battle Cruiser Squadron and the 1st Light Cruiser Squadron from Rosyth, and the 1st and 2nd Cruiser Squadrons and 4th Flotilla from Cromarty met the _Iron Duke_, and the 2nd and 4th Battle Squadrons at given rendezvous between Lat. 56.45 N., Long. 1.30., and Lat. 56.14 N., Long. 3.20 E. Vice-Admiral Sir Cecil Burney was under treatment on board a hospital ship and too unwell to take his squadron to sea. Admiral Sir Stanley Colville was, therefore, directed to hoist his flag on board the _Marlborough_ and to assume temporary command of the 1st Battle Squadron. The whole Fleet was together by 1.20 P.M. on the 25th, steering south-south-east at 15 knots. At 1.40 P.M. the _Birmingham_ and _Southampton_, of the 1st Light Cruiser Squadron, both sighted submarines about 15 miles to the south-westward of the Battle Fleet. The Battle Fleet was then gradually turned from the south-south-eastward course to north-north-eastward until 3 P.M., being then in position Lat. 56.22 N., Long. 3.43 E. Course was altered to north-north-west at 3.15 P.M. and speed reduced. At 9.15 P.M. the Fleet again turned to the southward, speed having to be reduced owing to the sea becoming too heavy for the destroyers. By midnight a south-westerly gale was blowing.