On February 6th, Foote formed his vessels into two lines, the ironclads--the _Cincinnati_, the _Carondelet_, the _Essex_, and the _St. Louis_--forming a front rank. Slowly and cautiously he approached the fort, firing as he went, the guns on the parapet answering those of the fleet. Several of the Confederate guns were disabled. The fleet was yet unhurt when the first hour had passed. Then a 24-pound shot struck the _Essex_, crashed through her side and penetrated her boiler, instantly killing both her pilots and flooding the vessel from stem to stern with scalding steam. The _Essex_, wholly disabled, drifted down stream, while her companion ships continued their advance and increased their fire. Presently, a sound exceeding the roar of cannon was heard above the tumult. A great gun in the fort had exploded, killing or disabling every man who served it. A great 10-inch columbiad was also destroyed. Tilghman, seeing that he had no hope of holding the fort, decided to save his army by sending it to Fort Donelson, on the Cumberland River. This he did, reserving fewer than a hundred men to work the guns. He then raised the white flag and surrendered the seventy-eight that remained. Grant had failed to reach the road to Fort Donelson until the Confederates had escaped. The Southerners hastened across the country and added their numbers to the defenders of Donelson--and by so doing they deferred surrender for ten days. Fort Donelson was a fortified enclosure of a hundred acres that crowned a plateau on the Cumberland River. It was just south of the boundary between Kentucky and Tennessee and close by the little village of Dover, consisting of a court-house, a two-story tavern, and a few houses scattered about. Beneath the bluff and on the river bank were two powerful batteries commanding the approach to the river. Outside the fort and stretching far along the ridges that enclosed it were rifle-pits, lines of logs covered with yellow clay. Farther beyond, the hillsides were covered with felled trees whose interlacing branches were supposed to render the approach of the foe impossible under fire. At this moment Donelson was held by eighteen thousand men under the command of General John B. Floyd, late Secretary of War in the cabinet of Buchanan. Next to him were Gideon J. Pillow and Simon B. Buckner. The Union army under Grant was divided into three parts under the respective commands of Charles F. Smith, a veteran of the regular army; John A. McClernand, an Illinois lawyer and member of Congress, and Lew Wallace, the future author of "Ben Hur."