INVESTMENT OF FORT DONELSON—THE NAVAL OPERATIONS—ATTACK OF THE ENEMY—ASSAULTING THE WORKS—SURRENDER OF THE FORT.PROMOTED MAJOR-GENERAL OF VOLUNTEERS—UNOCCUPIED TERRITORY—ADVANCE UPON NASHVILLE—SITUATION OF THE TROOPS—CONFEDERATE RETREAT—RELIEVED OF THE COMMAND—RESTORED TO THE COMMAND—GENERAL SMITH.CHAPTER XXIII.