Numbers 10. Reports of Captain John Johnson, C. S. Engineers, of operations August 12-23.

FORT SUMTER, August 15, 1863.

CAPTAIN: I have the honor to report for the law twenty-four hours, that a working force numbering 470 laborers and mechanics has been engaged int who reliefs, day and night, upon the defenses of the fort. The work accomplished consisted during the day of erecting two sand-bag traverses on eastern ramparts, and filing over the western magazine arches. The traverses were continued during the night, and one is very near completion, the one adjoining the 11-inch Dahlgren; the other is brought up to level of parapet. The carpenters and some force were also engaged during day in sawing up and taking away logs of crib work under east scarp wall, in order to make blindage for shelter of troops under gorge wall on interior of fort.

The night work accomplished was the discharging of some 3,000 bags of sand, being all received, and the building up of about 2,800 feet on exterior of gorge wall to a height in southwest re-entrant made by brick re-enforce of west magazine, of half the pitch of second-story rooms. This level is sustained for some 50 feet from the re-entrant eastwardly toward sally-port.

The fort was struck yesterday five times; twice in morning, 6 o'clock, from land Parrotts; once by shell, 11 a. m., from gunboat; twice again, 6.30 p. m., by land Parrotts. For particulars of damage, localities, penetration, &c., I beg leave to refer to memorandum now preparing, to be handed up to-morrow. I report with pleasure the arrival last night of two assistant engineers, Messrs. E. J. White and Mikell.

Respectfully submitted.

JNO. JOHNSON,

First Lieutenant, Engineer Corps.

Captain W. F. NANCE, Assistant Adjutant-General.

FORT SUMTER, August 15, 1863.

CAPTAIN: Herewith I have the honor to append descriptive memoranda of the different shots received by the fort during the fire from the enemy's land batteries on Morris Island and from the wooden gunboats during the 13th and 14th distant.

The batteries situated to the north and at the foot of Gregg's Hill, Morris Island, where the enemy have their observatory, are mounted chiefly with Parrott guns and two heavy mortars. I think there are eight or ten Parrotts, from 30-pounder upward.

On the morning of the 12th instant, they opened at not less than 5,000 yards with one 200-pounder Parrott, throwing shells weighing 150 pounds into and over the fort. A report of the damage sustained by the fort during that day was made by me to the chief engineer of South Carolina, Major Echols. Besides shell this gun threw solid beveled-top bolts, weighing, I suppose, the full 200 pounds, the caliber being 8 inches. The bunboats, two or three in number, lie off the east front of the fort on the prolongation of the gorge line, distant about 4,500 yards, apparently in the entrance of North Channel and