Organization of the Division of the Potomac, August 4, 1861.

Brigadier-General Hunter's brigade.-Twenty-third, Twenty-fifth, Thirty-fifth, and Thirty-seventh Regiments New York Volunteers.

Brigadier-General Heintzelman's brigade.-Fifth Regiment Maine Volunteers, Sixteenth, Twenty-sixth, and Twenty-seventh Regiments New York Volunteers, and Tidball's battery (A), Second U. S. Artillery.

Brigadier General W. T. Sherman's brigade.-Ninth and Fourteenth Regiments Massachusetts's Volunteers, De Kalb [Forty-first] Regiment New York Volunteers, Fourth Regiment Michigan Volunteers, Hamilton's battery (E), Third U. S. Artillery, and Company I, Second U. S. Cavalry.

Brigadier-General Kearny's brigade.-First, Second, and Third Regiments New Jersey Volunteers, Greene's battery (G), Second U. S. Artillery, and Company G, Second U. S. Cavalry.

Brigadier-General Hooker's brigade.-First and Eleventh Regiments Massachusetts Volunteers, Second Regiment, New Hampshire Volunteers, and Twenty-sixth Regiment Pennsylvania Volunteers.

Colonel Keyes' brigade.-Twenty-second, Twenty-fourth, and Thirtieth Regiments New York Volunteers, and Fourteenth Regiment New York State Militia [Eighty-fourth Volunteers].

Brigadier-General Franklin's brigade.-Fifteenth, Eighteenth, Thirty-first, and Thirty-Second Regiments New York Volunteers, Platt's battery (M), Second U. S. Artillery, and Company C [First], New York (Lincoln) Cavalry.

Colonel Blenker's brigade.-Eighth and Twenty-ninth Regiments New York Volunteers, Twenty-seventh Regiment Pennsylvania Volunteers, and Garibaldi Guard [Thirty-ninth], New York Volunteers.

Colonel Richardson's brigade.-Twelfth Regiment New York Volunteers and Second and Third Regiments Michigan Volunteers.

Brigadier-General Stone's brigade.-Thirty-fourth and Tammany [Forty-second] Regiments New York Volunteers, First Regiment Minnesota Volunteers, and Second Regiment New York State Militia [Eighty-second Volunteers].

Colonel William F. Smith's brigade.-Second and Third Regiments Vermont Volunteers, Sixth Regiment Maine Volunteers, Thirty-third Regiment New York Volunteers, Company H, Second U. S. Cavalry, and Captain Mott's New York battery.

Colonel Couch's brigade.-Second Regiment Rhode Island Volunteers, Seventh and Tenth Regiments Massachusetts Volunteers, and Thirty-sixth Regiment New York Volunteers.

The Second Regiment Maine, the Second Regiment Wisconsin, and the Thirteenth Regiment New York Volunteers, stationed at Fort Corcoran.

The Twenty-first Regiment New York Volunteers, stationed at Fort Runyon.

The Seventeenth Regiment New York Volunteers, stationed at Fort Ellsworth.

By October the new levies had arrived in sufficient numbers, and the process of organization so far carried on that the construction of divisions had been effected.

The following statement exhibits the composition of the Army, October 15, 1861:

Organization of the Army of the Potomac, October 15, 1861.

1. Brigadier General George Stoneman's cavalry command.-Fifth U. S. Cavalry, Fourth Pennsylvania Cavalry, Oneida Cavalry (first company), Eleventh Pennsylvania Cavalry (Harlan's), and Barker's Illinois Cavalry (one company).

2. Colonel H. J. Hunt's artillery reserve.-Batteries L, A, and B, Second U. S. Artillery; Batteries K and F, Third U. S. Artillery; Battery K, Fourth U. S. Artillery; Battery H, First U. S. Artillery, and Battery A, Fifth U. S. Artillery.

3. CITY GUARD, Brigadier General ANDREW PORTER.

Cavalry.-Companies A and E, Fourth U. S. Cavalry.

Artillery.-Battery K, Fifth U. S. Artillery.

Infantry.-Second and Third battalions U. S. Infantry, Company-Eighth and Company-First U. S. Infantry, and Sturges' rifles (Illinois Volunteers).

4. BANKS' DIVISION.

Cavalry.-Four companies Third Regiment New York Cavalry (Van Alen's).

Artillery.-Best's battery (F), Fourth U. S. Artillery; detachment Ninth New York