May 31st Commodore Schley made an attack upon the forts at the entrance to the harbor of Santiago, with the intention of ascertaining the position and strength of the fortifications. At one o'clock in the afternoon of that day the signal to form column was hoisted on the _Massachusetts_; the _New Orleans_, _Iowa_, and _Vixen_ followed her as she steamed slowly toward the harbor entrance. When between three and four miles from shore two of her 13-inch guns were fired; it is reported that one of the shells struck the partly dismantled Spanish war-ship _Reina Mercedes_, crashing through her bow and killing a number of men; two shots followed quite near the same vessel; the two guns in the forward turret sent their projectiles so close to the Spanish flagship that the spray was thrown all over her. The shore batteries at this time began a rapid fire on the _Massachusetts_, but she was soon beyond their range. The fire was then turned on the _New Orleans_; the shells from this vessel struck the large battery on the hill above Morro Castle, and a great cloud of dust and debris rose in the air as the shells burst. They must have done considerable damage; the shells which followed sent portions of the wall of Morro Castle tumbling down, a mass of ruins. Almost every shot found a mark in either the batteries or vessels. It was the _Iowa's_ turn next; her shells made things lively for the Spanish fleet in the harbor, although it is believed she was not successful in hitting any of the Spanish vessels. The little _Vixen_ swept along after her predecessors, and banged away with her one 6-pounder with as great an air of importance as if it had been a 13-inch rifle; then she steamed away in a triumphant manner, as much as to say: "I have done my share." The commodore promptly ordered her to keep out of danger. The ironclads turned, and a second time bore down on the harbor, and when within five miles the shells began again to fall thick and fast around the Spanish vessels, although accurate firing was almost out of the question, as the vessels were behind the hill out in sight, and range could not be ascertained. The Spaniards kept up a brisk cannonade long after our vessels had stopped firing; a tremendous amount of damage was done--to the Caribbean Sea; their shells did not come within a mile of our vessels. June 3d the auxiliary cruiser _St. Paul_ returned to New York, after a two weeks' cruise in West Indian waters; she had been detailed for guard and scout duty, and was one of the first to discover the Spanish fleet in Santiago Bay. She left Key West May 18th, and arrived off Santiago about the 20th. The St. Louis had been detailed for similar service, and had been watching Santiago harbor with the expectation that the Spanish vessels would attempt to enter there; she, however, left on the 19th. It is supposed that Admiral Cervera must have entered the harbor in the twenty-four hours between this date and that of the arrival of the _St. Paul_.