Grant, having completed the investment of Vicksburg, sent word on the evening of the 21st that he intended to make a general assault upon the enemy's works at 10 A.M. the following day, and asked that the fleet might shell the batteries from 9.30 to 10.30. Porter complied by keeping up his mortar fire all night and sending up the gunboats to shell the water batteries, and other places where he thought the enemy might find rest. At 7 A.M. the next day the Mound City, followed at eight by the Benton, Tuscumbia, and Carondelot, moved up abreast the lower end of the canal, opening upon the hill batteries; then they attacked the water batteries, the duel between them and the ships at a range of four hundred and fifty yards being maintained incessantly for two hours. The Tuscumbia proved, as before, too weak to withstand such close action and had to drop down. The admiral wrote that this was the hottest fire that the gunboats had yet endured, but the water batteries having little elevation, the ships contended on more even terms than at Grand Gulf, and fighting bows on, received little damage. The fire was maintained for an hour longer than Grant had asked, when the vessels dropped out of range, having lost only a few wounded. The assault of the army was not successful and regular siege operations were begun. Vicksburg and Port Hudson, the two extremes of the Confederate line, were thus formally invested by the 27th of May. On that day, Porter, having received a request from Grant and Sherman to try whether the enemy had moved from the batteries the guns on their extreme left, as they had from many of the other hill batteries, sent down the gunboat Cincinnati, Lieutenant George M. Bache, to draw their fire if still there; and, if possible, to enfilade the enemy's rifle-pits in that quarter and drive them out. The Cincinnati started from the upper division of the squadron at 7 A.M.; the vessels of the lower division, Price, Benton, Mound City, and Carondelet, steaming up at the same time to cover her movement by engaging the lower batteries, which might have played upon her. General Sherman took a position upon a hill at the extreme right of the Union lines, overlooking the river, so as to see the affair and take advantage of any success gained by the Cincinnati's attack. The gunboat, protected as usual by logs and hay, came within range shortly after nine o'clock, and the enemy began firing rapidly from all their batteries, the guns whose position had been doubted proving to be in their old place. When abreast the position assigned her for enfilading the rifle-pits the Cincinnati rounded to, and as she did so a shot pierced her side and entered the shell-room, capsizing nearly all the boxes on one side of the alley. As she came to with her head up stream, another ball entered the shell-room below the water-line, and a third pierced her stern, always the weakest part of these vessels, going into the