Quincy A. Gillmore to Thomas W. Sherman, December 1, 1861

Brig. Gen. THOMAS W. SHERMAN,

Commanding Expeditionary Corps, Hilton Head, S. O.:

SIR : Agreeably to your orders I proceeded in the steamer Ben DeFord, on the afternoon of the 29th ultimo, to Tybee Island, to make a military examination of that locality. We arrived at the Tybee light-house about 7 p. m., when I called upon the senior naval officer present, and made arrangements with him for disembarking my escort (three companies of the Fourth New Hamphshire Volunteers, under Major Drew) at

7 o’elock on the following morning. There was some delay in landing, so that I was not ready to commence the work of the day before 9 a. m.

I first endeavored to de;ermine the prominent topographical features of the island, and found that at high water it is nearly divided into two parts by a marsh, or rather two marshes, which make up from the inlet or creek which bounds the island on the southwest. ‘This marsh, or a great part of it, is slightly submerged at high tide, and is difficult to pass even at low water. Men might pick their way across it, but troops could not maneuver on it. To pass from the northwest point of the island, opposite Fort Pulaski, to the southeast part, at the mouth of the inlet, I found it necessary to come back within 300 yards of the lighthouse.

On the west end of Tybee Island, opposite Fort Pulaski, a parapet for infantry 100 yards long has been thrown across the neck of land to prevent troops from approaching from the direction of the light house. West of this troops have been encamped in bush tents. In a southwesterly direetion on the other side of the creek the land appears to be low and marshy, except a small area in a southerly direction from the earthwork, occupied by a house. Returning to the old tower near the light-house, I took its principal dimensions and those of the unfinished earthwork which surrounds it. The tower is built of shell concrete ; its walls are high, with but one opening (4 feet wide) to the exterior. In it is a good magazine 6 by 7 feet and 7 feet high, with brick walls 3$ feet thick. The second story is about 9 feet high, and has one communication with the exterior. It is on the west side. The third story is pierced with twelve loop-holes, at equal distances apart, 1 by 1 foot at the throat and 2 by 2 feet on the exterior. Four fire-places exist on this story. Above the floor covering the third story the wall is carried up flush with the inside, so as to form a breast-height 4 feet thick and 44 feet high.

The tower is surrounded by an unfinished field work, which could with little labor be made a strong position, that would control the prineipal entrance to Savannah River, and thus render efficient services to the blockade in case the fleet should be driven off by stress of weather. One or two siege guns could be mounted on the tower.

I give a rough sketch of the tower and its surroundings.

I proceeded to the southern point of the island along the main shore and thence up the inlet on the southwest, in order to get a near view, if possible, of the battery which controls Warsaw Inlet. My guide (Mr. Ferguson, of the steamer Flag) is of opinion that this battery contains four guns and is located on the second Tybee Island, as it had been firing seaward the day before, when he was on the south point of North Tybee, and had a very good opportunity to judge. A large derrick, plainly visible, with all its rigging, had been erected since he last saw it. I am unabie to say whether he is correct or not, and three naval officers with whom I conversed could furnish me with no positive information on the subject. Its thorough examination can only be made by using boats, either directly from the sea or by passing over to the second Tybee Island. To do this would have detained me from Hilton Head all of to-day and a portion of Miete all of) to-mcrrow, as the pilot of the Ben DeFord requires daylight to navigate his ship in. My hurried departure on Friday left my duties here in a condition that would not warrant so lengthy an absence. I therefore thought it proper to report to you for further orders.

The exact position of the battery controlling Warsaw Inlet has, however,no bearing on the prominent points to which my attention was directed in your verbal instructions, viz, the propriety of occupying and holding the first Tybee Island, and the practicability (and, if deemed practicable, the best method) of reducing Fort Pulaski. I deem the reduction of that work practicable by batteries of mortars and rifled guns established on Tybee Island. I think it probable that a nearer position on firm ground (though very shallow, and therefore ill-adapted to moriar and sunken batteries) can be found on the island west of Tybee. I would establish these batteries from 20 to 25 yards apart, one gun or one mortar in each, behind the ridge of sand on the shore, westward from the light-house. I would sink the mortar batteries as low as the water would permit, and the guns sufficiently low to leave a high parapet in front. On the sides and rear of each I would have a high mound of earth, and I should cover each with a horizontal bombproof shelter of logs, covered with earth, and supported by logs planted vertically in the ground. The embrasures for the guns should be deep, narrow, and of very little splay. I estimate that after once obtaining the range five-eighths of the shells from mortars can be lodged inside of the fort. I would have enough mortars to throw one shell a minute into the fort, and as many guns as mortars. ‘The batteries should operate day and night. For landing the ordnance required for these operations I would have built two or three broad flat-bottomed bateaux Or scows, such as are commonly used on rope ferries. I think these eould be built here.

There are now probably at Fort Pulaski 700 good troops. About 200 landed yesterday, and the Navy officers informed me that at least 500 have entered the fort within the last three days, while some (probably raw recruits or portions of the Home Guard) have gone away. It may be their design to land on Tybee and hold the west end of it, to prevent tue erection of batteries against the fort. I therefore recommend the immediate occupation of Tybee Island by one good regiment until the question of attempting the reduction of Fort Pulaski be determined.

ilearned while at Tybee that offers have been made by negroes to burn two of the principal bridges on the railroad between Charleston and Savannah. One of these bridges is said to be nearly two miles long. In a military point of view its destruction would be of great vaiue to us, and I recommend the subject to your attention.

Very respectfully, your obedient servant,