DECEMBER 9, 1863.-Mutiny at Fort Jackson, La.

Reports of Major General Nathaniel P. Banks, U. S. Army, and record of Military Commission.

HEADQUARTERS DEPARTMENT OF THE GULF,
New Orleans, December 11, 1863.

GENERAL: An unpleasant affair occurred at Fort Jackson on the evening of the 9th instant. Lieutenant-Colonel Benedict, of the Fourth Regiment, Corps d'Afrique, having some difficulty with the troops there, struck and punished 2 soldiers with a whip.

This produced great excitement among the troops, who assembled on the parade grounds, in most violent excitement, and threatened the officers of the regiment. They fired their muskets in the air, and committed other excesses, but without doing any injury to persons or property. This occurred about 6.30 o'clock. Colonel Drew, in command of the post, reports that the excitement continued about half an hour, when they were quieted, and at tattoo all were in their quarters. The next morning at reveille every man is reported to have answered to his name. The negroes have been constantly assured, whether engaging in labor or enlisting as soldiers, that under no circumstances whatever were they to be subjected to the degrading punishment of flogging. This has always been made a condition by them, and they have always received this assurance from the officers of the Government.

Lieutenant-Colonel Benedict, being ordered to report to these headquarters, tendered his resignation, which was not accepted. A military commission, consisting of Major-General Herron, Colonel Horace B. Sergeant, and Captain Stephen Hoyt, with Major Lieber as judge-advocate, has been appointed to make through investigation of all the facts connected with the affair. The order appointing the commission, with its instructions, are inclosed herewith.

The captain of the steamer Suffolk, lying near Fort Jackson, became greatly alarmed at the demonstrations made, and moved up to the Quarantine Station, sending from there exciting telegraphic dispatches to these headquarters.

It was difficult to get precise knowledge of affairs during the night, but, with a view of being on the safe side, Commodore [Henry H.] Bell was requested to send one or two more gunboats immediately to Fort Jackson. A regiment of troops was moved down during the evening and a battery of artillery in the morning. They proceeded no farther than Quarantine Station. Commodore Bell himself moved down the river with the Pensacola.

Many exciting rumors have been started in the city concerning this affair, and it is quite possible they may be reproduced in the north. It is proper for me to say, therefore, that however unfortunate the occurrence may have been, and whatever guilt may be attached to the different parties concerned, there is nothing to excite apprehension or to suggest a doubt as to the perfect confidence with the Government may repose in troops of this class. There were no prisoners, either of the rebel or our own army, at Fort Jackson, and no inconvenience has been experienced, excepting that which arose from the imperfect knowledge of the events of the evening and the excitement produced by an occurrence of this character. Elsewhere in the department everything is quiet.

Inclosed I send copies of the various dispatches received and sent to the captain of the Suffolk and other officers at Quarantine Station, Fort