HEADQUARTERS DEPARTMENT OF THE SOUTH,
Hilton Head, S. C., July 25, 1864.

GENERAL: I have nothing important to communicate since my last report. The bombardment of Fort Sumter and the city is maintained slowly. I am extending Battery Putnam and connecting it with Battery Chatfield, so as to obtain positions for a larger number of guns bearing on Fort Sumter and the channel. We have already knocked down the temporary defenses erected by the rebels on top of the ruins of Sumter and have also scraped off the ruins at one point of the gorge, so as to make the ascent practicable from the water's edge. The northeast storm that has prevailed for several days has put a stop to the operations of the mine rafts as well as to all military movements by water. I hoped to have received aid from the monitors in floating these rafts against the fort, but I found after some delay that the officers entertained so many objections to going as near the fort as I judged necessary for effect, say 1,000 yards, that I was forced to give up the idea of their assistance. I then turned the rafts over to the boat infantry on shore to operate. I do not think that Admiral Dahlgren intends to undertake, on his own responsibility, any offensive operations with the iron-clads.

I have ascertained much with regard to the present condition of Fort Sumter from deserters. The summary of all this is as follows, viz: The lower tier of casemates is generally still intact and habitable, being used as quarters for officers and men, store-rooms, magazine, and gun-roads. The top of the arches of this tier is covered with the debris from the second tier and parapet, and is nearly bomb-proof. The ends of the arches toward the parade are closed up by the ruins of the upper wall, and are thus effectually protected from shot or shell. A communication extends all around in this tier from casemate to casemate, even through the ruins of the gorge. The earth has been taken out of the parade to put upon the arches and bob-proofs and to build traverses. A walk of 3 or 4 feet width only is left around the edges. The water in the space thus dug out is about 4 feet deep. A plank walk extends across this from the sally-port, which is on the left bank near the shoulder angle, to the battery, as it is called, which is on the right face near the angle and consists of three guns. In rear of this, on the parade and covering the casemates, in which are the guns, is a large bomb-proof, constructed of timber and covered with earth. Two more guns are in casemates on the left face near the shoulder angle. One of these is fired as evening gun.

The sally-port is formed by enlarging an embrasure on the left flank near the shoulder angle. It has strong gates and opens upon a floating wharf. The magazine is now situated in the right shoulder angle of the fort. The old magazine in the left gorge angle was blown up accidentally some time ago. There are four light field pieces, 12-pounder howitzers, which are hauled to the top of the ruins every night to be used in case of assault. Hand-grenades of the improved pattern are also issued to the guard on the wall each night. This guard is about 100 men. The garrison numbers 250 men, and is relieved every two or three weeks. Captain Mitchel, the son of the Irish patriot, now commands. Temporary obstructions are placed upon the ruins at night, and removed before daylight. There is the fragment of a boom still in front of the right face. No torpedoes are around the fort.