7 o'clock 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 determine 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 light-house.

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 direction 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 10 feet thick, and it is three stories in height. The first story is 9 feet 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 1/3 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 4 1/2 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 principal 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 unable 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 (perhaps all of) to-morrow, 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