of principal military interest in this vicinity during the past month, including such information as I have been able to collect in regard to the movements of the enemy in our front, the force opposed to us, the position of their camps, &c., I have the honor to submit the following:

During the past month I have learned but little in addition to the information I already possessed and have communicated to you concerning the situation and strength of the enemy's forces in my immediate front. Colquitt's brigade, which was formerly encamped on James Island, near Secessionville, went to Florida with Beauregard in January, and has not yet returned. The troops at present on the island are Hagood's brigade, not over 3,000 strong, and a regiment or two besides. On Sullivan's Island there is less than a brigade (some 2,000 men), under command of Colonel Keitt. Not more than a regiment is seen drilling at any time on the beach. There is one battalion in the city of Charleston. Sumter, James Island, Mount Pleasant, and Charleston are all connected by submarine cables. There are but few pickets on the water front of the city. The only points at which sentries are stationed, as far as I can learn, are at the foot of Tradd Street, at Chisolm's Mills, and at two small batteries and one wharf on Cooper River. They have three iron-clads afloat four guns in each. One of them is the Chicora, whose machinery is out of order and in dry-dock being repaired. The garrison in Sumter consist of from 250 to 300 men, artillery and infantry, and is changed every fifteen days.

The enemy is strengthening Castle Pinckney, which now mounts three 10-inch columbiads and one rifle, and Ripley mounts two guns. They talk of mounting a gun at Sumter for the purpose of firing at our calcium light at Gregg. The "big gun" in Charleston is mounted on Frazer's wharf, and not long ago a solid shot was fired from it as far as Castle Pinckney; shell a good deal farther.

I learn from deserters that after the destruction of the blockade-runner Presto on the 2nd February the troops on Sullivan's Island got hold of the liquor on board of her and had a "grand drunk." and it is alleged that 300 men at that time could have taken the island, but unfortunately it was not known until the opportunity has passed.

During the month of March I find the following work to have been done and alterations made on rebel batteries in and around Charleston Harbor:

The northeast front of Battery Marshall, on the east end of Sullivan's Island, has been strengthened with sand and sod and the magazines repaired. There is now being built a parapet on the sea front and they have one pivot gun in position on that face. They seem to be changing somewhat this battery so as to give it more command over Long Island.

There has been no visible change in the three two-gun batteries between Marshall and Beauregard.

A new traverse has been built at the west and of Fort Beauregard, behind which I think, a guns has been mounted. A new gun (a columbiad, I think) has been mounted near the center of the fort. There has been considerable work done just to the rear of the spot where the Moultrie House stood, but it has not assumed sufficient shape to determine what they intend building, but I presume a mortar battery. Near this place two platforms have been built on which are two pieces of light artillery.