HEADQUARTERS DEPARTMENT OF THE SOUTH, Hilton Head, S. C., February 9, 1865.

Major General Q. A. GILLMORE:

GENERAL: In turning over the command of the Department of the South to you I herewith place in your hands the instructions, both public and confidential, received from the War Department and from General Sherman. General Sherman's written instructions may be modified in execution, if the circumstances warrant it; for instance, if the enemy show a disposition to evacuate Charleston he may be left strongly, and if the evacuation actually takes place the works are to be occupied and the diversion in Bull's Bay may not then be made. Secondly. After carrying out the instructions regarding the operations at Bull's Bay, if, in the judgment of the commander of the department, an additional operation may be attempted on Sullivan's Island, as the admiral desires, he may undertaken if it circumstances be favorable. This must not, however, be t othe prejudice of anything specially directed by General Sherman. Brigadier General J. P. Hatch is to follow the enemy toward Charleston with his whole and destroy completely the railroad as far as he can go. This ought to be done as far as the Ashepoo if possible, and under very favorable circumstances to the Edisto. He is at the same time aided by Brigadier General Henry Prince, commanding camp of detachments for General Sherman's army at Blair's landing, on the Pocotaligo River, to guard General Sherman's communication back to Port Royal, at least from the railroad back to that place. General Price is under command of the general commanding the department. If the city of Charleston be evacuated the destruction of the railroad is to be stopped, as we may need it for use. General Hatch may then be withdrawn, leaving a sufficient guard at Port Royal Ferry, Pocotaligo,&c. As soon as General Sherman reaches the triangle between Columbia, Camden, and Kinston, this same force may also be withdrawn, then be used elsewhere. The orders from General Grain a camp at or near Pocotaligo, and no limit is fixed to this maintenance. General Sherman desired a picket to be kept at Coosawhatchie, Salkehatchie bridge, and Combahee Ferry, with a reserve at Garden's Corners, and wherever else necessary, with main body at camp at or near Pocotaligo. As far as operations in Charleston Harbor is concerned, the commander of the department may co-operate with the admiral in any way that he may judge proper, provided the written instructions be first fully carried out. General Sherman did not favor any serious operation about Charleston Harbor, but was willing to yield his objections if the commanding officer, after carrying out his essential directions, judged he had on opportunity favorable enough to warrant the risk of a serious attack. General Sherman attached more importance to the flank movement at Bull's Bay and Georgetown. Major Gray informed me that General Sherman desired the operations at Bull's Bay to be made six days from that day (the 8th instant). The force for this is assembled at the StoNumbers The present position of affairs with respect to General Saxton is seen by reference to letters on file. General Saxton has to-day replied to my letter of the 4th instant requesting that he state officially what aid an assistance he requires to enable him to perform his duties. This letter is left for your action. I have also made application to the Secretary of War to have the last sentence of paragraph V, of Special Field Orders, No. 15, issued by General Sherman, annulled, so as to leave the recruiting and organization of the negroes where it rested by previous orders and instructions of the War Department.