OFFICE CHIEF ENGINEER DEFENSES MEMPHIS, VICKSBURG, AND NATCHEZ,

Vicksburg, Miss., March 16, 1864.

Major General J. B. McPHERSON:

SIR: In accordance with your directions, I have the honor to make the following report of number of troops necessary for the garrison of this post and of Natchez, Miss.:

The development of the interior crest of the line at Vicksburg is about 10,000 yards in length, and will require for its defenses, at the least calculation, 7,500 men. It may be divided as follows: First, commencing on the right at the bank of the river, and following the line by way of Fort Grant, Castle Fort, Cherry street, and battery on Crawford street to the valley terminating in rear of the jail. This part will require a garrison or 2,000 men, with a reserve of 500, which will be located between Castle Fort and Fort Grant, the key points of that part of the line.

The second division will run from the termination of the first, by way of Fort McPherson and Jackson road, to Fort Sherman on Glass Bayou; this will require a garrison of 2,000 man, with a reserve of 500, the latter to be posted about midway between Forts McPherson and Sherman.

The third division extends from Glass Bayou along the ridge opposite Fort Sherman to the north fort; thence to the Spanish Fort; thence to the river. This is the most importance part ot the line, for if gained by the enemy, it would command the other part of our line, the town, and the river; it should be garrisoned by at least 2,000 men, with a reserve of 500, the latter to be located in the vicinity of the Spanish Fort, and composed of the best troops in the garrison. This furnishes a complete line around Vicksburg, and I think could be held against any force the enemy can bring to bear upon it with the garrison as estimated.

Fort McPherson, at Natchez, is more as an entrenched camp than for the actual protection of the town. The development of the interior crest is about 10,000 feet in length, and will require a garrison of at least 2,500 man to man the line, and a reserve of 500, the key points being the work at the hospital and the one on the former site of Susette's house. An interior line has been constructed, to which, in case of disaster, the troops could fall back and hold with 1,000 men.

I would respectfully suggest that in case the garrison is reduced to the minimum, 3,000 that the officers in charge of the quartermaster's commissary, and ordnance departments be instructed to move their depots inside of the work.

I am, general, very respectfully, your obedient servant,

JOHN M. WILSON,

Captain, Engineers.

HEADQUARTERS,
Nashville, March 16, 1864.

Major General F. P. BLAIR, Washington, D. C.:

Why not the Seventeenth, the command of which is now vacant, instead of the Fifteenth Corps?

U. S. GRANT,

Lieutenant-General.

6 R R-VOL XXXII, PT III