once. I wait for it to go to Hilton Head, to which point Major-General Foster orders me to send one of my regiments. After that is done the locomotive might be sent down to Callahan after the locomotive and train. A previous reconnaissance should be made, however, to ascertain the condition of the track, and whether the train is there or not, and whether it can be moved. I sent up a company probably reach that place to-night. To-day I ordered a reconnaissance from Fernandina as far as Callahan. The company from Yellow Bluff has orders to look after the locomotive and train. it would be well for you, however, to send down some cavalry to examine the track, especially the bridges, and an engineer can run up the locomotive. It is possible the rebels may not have injured it at all. I attach great importance to closing up thoroughly all the defiles and ferries and crossing from the front to your position.

Baldwin is the key to the possession of Florida, and if the enemy can re-enforce he will attempt to retake it. Destroy completely the trestle-work over the South Fork of the Saint Mary's. Block up with felled trees the fords over Brandy Creek, Big Creek, Yellow Water, &c., leaving but one avenue open to the front, which you must have well picketed. Since the order from Hilton Head has put an end to all further enterprises for the present, keep all the troops, except the Eight U. S. Colored Troops; familiarize the cavalry with the country and the neighborhood, letting the horses and men have rest to prepare them for future movements, which are possible after my return from Hilton Head. The fort should be a model of strength, and should inclose an excellent well of water. Make it impregnable. I think we shall have time to put up a good one.

Very respectfully, your obedient servant,

WM. BIRNEY,

Brigadier-General, Commanding.

P. S.-I shall leave for Hilton Head to-morrow, the 29th instant.

HILTON HEAD, S. C., July 28,1 864.

General FOSTER:

The Wabash goes to sea to-day, leaving the brig containing rebel prisoners without protection. Would advise she be moved under cover of the guns of the New Hampshire.

DAHLGREN,

Admiral.

HEADQUARTERS DEPARTMENT OF THE SOUTH, Hilton Head, S. C., July 29 1864.

Major General SAMUEL JONES,
Commanding Confederate Forces, Dept. of S. C., Ga., and Fla.:

GENERAL: I have the honor to inform you that the Secretary of War has authorized me to exchange any prisoners in my hands, rank for rank, or their equivalents; such exchange being a special one. In accordance with the above I send Major Anderson to make arrangements as to time and place for the exchange.

I have the honor to be, very respectfully, your obedient servant,

J. G. FOSTER,

Major-General, Commanding.