Passage: At the outbreak of the First World War, Von der Tann was serving as the flagship of the 3rd Admiral of Reconnaissance Forces, Konteradmiral Tapken. The ship was assigned to  I Scouting Group of the High Seas Fleet, under the command of Rear Admiral Franz Hipper. Von der Tann's first major sortie during the war occurred when the ship took part in the unsuccessful search for British battlecruisers, after the Battle of Heligoland Bight, in August 1914. During the Battle of Heligoland Bight, Von der Tann had been stationed in Wilhelmshaven Roads, and had been ordered to raise steam as early as 08:20, to assist the German cruisers under attack in the Heligoland Bight. At 08:50, Rear Admiral Hipper requested permission from Admiral von Ingenohl, the commander in chief of the High Seas Fleet, to send Von der Tann and Moltke to relieve the beleaguered German cruisers.Von der Tann was ready to sail by 10:15, more than an hour before the British battlecruisers arrived on the scene. However, the ship was held up by low tide, which prevented the battlecruisers from crossing the bar at the mouth of the Jade Estuary. At 14:10, Von der Tann and Moltke were able to cross the Jade bar, and Hipper ordered the German light cruisers to fall back on the two heavy ships, while Hipper himself was about an hour behind in the battlecruiser Seydlitz. At 14:25, the remaining light cruisers, Strassburg, Stettin, Frauenlob, Stralsund, and Ariadne, rendezvoused with the battlecruisers. Seydlitz arrived on the scene by 15:10; Ariadne succumbed to battle damage and sank. Hipper ventured forth cautiously to search for the two missing light cruisers, Mainz and Cöln. By 16:00, the German flotilla began returning to the Jade Estuary, arriving at approximately 20:23.Later that year Von der Tann was present at the Raid on Yarmouth, on 2–3 November. At 16:30 on the 2nd, Von der Tann, along with Seydlitz (Hipper's flagship), Moltke, the armored cruiser Blücher, and the four light cruisers Strassburg, Graudenz, Kolberg, and Stralsund, departed the...

Question: What were the names of the two missing cruisers?
Mainz and Cöln