But, on reaching the city, he found that the energetic admiral had already started out to clear the river of the Confederate batteries that lined it on either side as far up as Vicksburg. This was a service of no little danger, and one bringing but little satisfaction; for no sooner had the gunboats left one point, from which by hard firing they had driven the Confederates, than the latter would return in force, build up again their shattered earthworks, mount new guns, and be once more ready for battle. But more powerful than these little one or two gun-batteries were the Confederate works at Port Hudson, the destruction of which was absolutely necessary for further Union successes on the great river. Between Port Hudson and Vicksburg, the river was completely under the control of the Confederates; and it was a powerful gunboat that could hope to navigate that stretch of water unharmed. Farragut determined to attack Port Hudson, and set the 14th of March, 1863, as the date for the action. Port Hudson batteries were perched on a high bluff that overlooks one of those abrupt curves around which the current of the Mississippi River sweeps with such terrific force. The heavy guns bore down upon a point at which the ships would almost inevitably be swept out of their course by the swift stream, and where the river was filled with treacherous shifting shoals. Naval officers all agreed that to pass those batteries was a more difficult task than had been the passage of the forts below New Orleans; yet Farragut, eager to get at the stronghold of the foe in Vicksburg, determined to make the attempt. The mortar-vessels were stationed below to drive the enemy from his guns with well-directed bombs; while the fleet, led by the stanch old "Hartford," should make a bold dash up the river.