II. Captain Horace Porter, U. S. Ordnance Department, is announced as an aide-de-camp to Lieutenant-General Grant, with the rank of lieutenant-colonel.

By order of the Secretary of War:

E. D. TOWNSEND,

Assistant Adjutant-General.

GENERAL ORDERS, HDQRS. TWENTY-THIRD ARMY CORPS,

Numbers 20.
Bull's Gap, Tenn., April 4, 1864.

In order to comply with instructions from the headquarters of the Division of the Mississippi, the undersigned hereby relinquishes the command, temporarily, of the Twenty-third Army Corps.

When he assumed command of the corps, he expected and intended to make its headquarters his home during the rebellion, but other duties render this now inexpedient.

In parting with the officers and enlisted men with whom he has been so short a time associated, he takes the occasion to state that in a long and varied service in the army he has never had the honor to command any body of troops which, for bravery, loyalty, and devotion, for intelligence, energy, and zeal, and for all that constitutes the citizen, the soldier, and the patriot, can claim superiority over the corps from which he now relinquishes control, and feels the assurance that your future will not belie the past. And he also takes the occasion to reaming you that we have each and all taken upon us the solemn obligation to obey all orders of our superiors, and that we are engaged in a contest for the supremacy of law and the rights of man.

GEORGE STONEMAN,

Major-General.

GENERAL ORDERS, HDQRS. TWENTY-THIRD ARMY CORPS,

Numbers 21.
Bull's Gap, Tenn., April 4, 1864.

In pursuance of paragraph III, Special Orders, Numbers 94, current series, from headquarters Department of the Ohio, the undersigned hereby assumes command of the Third Division, Twenty-third Army Corps, and also as senior officer present assumes command of the Twenty-third Army Corps during the absence of Major General George Stoneman, who relinquishes the command temporarily in compliance with instructions from headquarters Military Division of the Mississippi.

J. D. COX,

Brigadier-General, U. S. Volunteers.

SPECIAL ORDERS, HDQRS. SEVENTEENTH ARMY CORPS,

Numbers 91.
Vicksburg, Miss., April 4, 1864.

The following is the organization of the Post and Defenses of Vicksburg, Brigadier General J. McArthur commanding:

Garrison proper, to be borne on post returns:

First. The Seventh Missouri Infantry, Seventeenth Illinois Infantry,