CIRCULAR.] Headquarters Army of the Potomac, July 19, 1863.

The following movements of troops are ordered for to-morrow, July 20, 1863:

1. The Third Corps will move promptly at 4 a. m., pass through Snickersville, and take position at or in the vicinity of Upperville, on the pike from Ashby's Gap to Aldie.

2. The Second Corps will move by the direct route to Bloomfield, and take position there.

3. The Twelfth Corps will move to Snickersville, and take position there.

4. The Fifth Corps will move promptly at 4 a. m., pass through Union, and along the road to Rectortown, taking position at or in the vicinity of the point where the road to Rectortown intersects the pike from Ashby's Gap to Aldie.

5. The Reserve Artillery will follow the Fifth Corps at 10 a. m., or sooner, if the road is clear, and, after passing through Union, will be parked at the first suitable ground.

6. The Sixth Corps will move at 10 a. m., follow the same route as the Fifth Corps, and halt, after crossing the Snickersville and Aldie pike.

7. The First Corps will move promptly at 4 a. m., taking the route to Middleburg, leaving Philomont on the right, and will take position at or in the vicinity of Middleburg.

8. The Eleventh Corps will follow the First Corps as soon as the road is clear, and take position near the crossing of Goose Creek, by the Snickersville and Aldie pike.

9. Those corps the hour of march for which is not fixed will move as soon as the column in front is fully in motion. Corps commanders will keep themselves informed upon this point, and will see that every effort is made to move all parts of their commands promptly and to keep the columns well closed.

10. Headquarters will be established in the vicinity of Union.

By command of Major-General Meade:

S. WILLIAMS,

Assistant Adjutant-General.

HARPER'S FERRY, VA., July 19, 1863-10 p. m.

Colonel DONN PIATT,

Chief of Staff, Baltimore, Md.:

I have as follows: First Potomac Home Brigade, Maryland Volunteers, Colonel Maulsby; First Eastern Shore Maryland Volunteers, Colonel Wallace; Second Eastern Shore Maryland Volunteers, Colonel Rodgers; One hundred and seventy-seventh Pennsylvania Volunteers, Colonel Wiestling; One hundred and seventy-fifth Pennsylvania Volunteers, Colonel Dyer; Eighth New York Volunteer Artillery, Colonel Porter; Ninth Maryland Volunteers, Lieutenant-Colonel Simpson; Tenth Maryland Volunteers, Lieutenant-Colonel Ross; Thirty-fourth Massachusetts Volunteers, Colonel Wells; Snow's (Maryland) battery; Seventeenth Indiana Battery, Captain Miner; Battery C., First Pennsylvania Artillery, Lieutenant Rosney; 343 Connecticut and Michigan cavalry, and Duvall's cavalry.

HENRY H. LOCKWOOD,

Brigadier-General, Commanding.