Lookouts on the _Guerrière_ reported to Decatur that a despatch-boat had left Gibraltar as soon as the American ships appeared, and inquiry led the captain to believe the boat was bearing messages to Reis Hammida. Other boats were sailing for Algiers, and Decatur, realizing the ease with which his wily opponent, thoroughly familiar with the inland sea, would be able to elude him, decided to give chase at once. The fleet headed up the Mediterranean June 15th, under full sail. The next evening ships were seen near shore, and Decatur ordered the frigate _Macedonian_ and two brigs to overhaul them. Early the following morning, when the fleet was about twenty miles out from Cape Gata, Captain Gordon, of the frigate _Constellation_, sighted a big vessel flying the flag of Algiers, and signaled "An enemy to the southeast." Decatur saw that the strange ship had a good start of his fleet, and was within thirty hours' run of Algiers. He suspected that her captain might not have detected the fleet as American, and ordered the _Constellation_ back to her position abeam of his flag-ship, gave directions to try to conceal the identity of his squadron, and stole up on the stranger. The latter was seen to be a frigate, lying to under small sail, as if waiting for some message from the African shore near at hand. One of the commanders asked permission to give chase, but Decatur signaled back "Do nothing to excite suspicion." The Moorish frigate held her position near shore while the American ships drew closer. When they were about a mile distant a quartermaster on the _Constellation_, by mistake, hoisted a United States flag. To cover this blunder the other ships were immediately ordered to fly English flags. But the crew of the Moorish frigate had seen the flag on the _Constellation_, and instantly swarmed out on the yard-arms, and had the sails set for flight. They were splendid seamen, and almost immediately the frigate was leaping under all her canvas for Algiers. The Americans were busy too. The rigging of each ship was filled with sailors, working out on the yards, the decks rang with commands, and messages were signaled from the flag-ship to the captains. Decatur crowded on all sail, fearing that the Algerine frigate might escape him in the night or seek refuge in some friendly harbor, and the American squadron raced along at top speed, just as the Barbary pirates had earlier chased after the little brig _Edwin_, of Salem. Soon the _Constellation_, which was to the south of the fleet and so nearest to the Moorish frigate, opened fire and sent several shots on board the enemy. The latter immediately came about, and headed northeast, as if making for the port of Carthagena. The Americans also tacked, and gained by this manoeuvre, the sloop _Ontario_ cutting across the Moor's course, and the _Guerrière_ being brought close enough for musketry fire.