HDQRS. THIRD ARMY CORPS, ARMY OF VIRGINIA, Warrenton, Va., July 21, 1862.

Major General N. P. BANKS,
Commanding Second Army Corps, &c.,

Headquarters six miles east of Sperryville:

GENERAL: I received a few hours since a copy of your dispatch of 20th instant to Major-General Pope, and am instructed by him to communicate with you concerning matters in our front. I take advantage of the return of your messenger to write you this note and request information as to the situation of our forces and the supposed position of the enemy. All that I have of either is from your dispatch above referred to.

By the order of the major-general commanding my cavalry brigade (two regiments) went to Culpeper, there to join General Hatch, and I have no report from its commander.

Will you please inform me, general, if in your power, what is the position of the First Corps as well as your own? I have one division (King's) at Fredericksburg, and, as you know, my Second Division here.

I have the honor to be, general, very respectfully, your most obedient servant,

IRVIN McDOWELL,

Major-General, Commanding.

HEADQUARTERS SECOND ARMY CORPS, Near Washington, July 21, 1862-1.45 p. m.

Major-General McDOWELL,
Commanding Corps d'Armee, Warrenton, Va.:

MY DEAR SIR: Has I known you were at Warrenton I should have written you earlier. In answer to your note, which I received by my messenger, I have the honor to report that my corps is encamped on the Sperryville and Warrenton turnpike, 6 miles from Sperryville and I east of Washington, fronting toward Culpeper. General Hatch, with our whole cavalry force, occupies Culpeper. There are three regiments of infantry also in that neighborhood under his command. His instructions are to watch and harass the enemy supposed to be at Gordonsville under Ewell, and represented to be 6,000 strong.

I was my purpose, and more in accordance with my orders, to have placed my corps on the direct road from Sperryville to Amissville, which is shown by the maps, but my engineers, who selected the ground, reported this road wholly impracticable for moving trains or wagons, and not adapted to the purposes which I was to aid in carrying out. A second reconnaissance confirms his report. I am therefore on the direct road from Sperryville to Warrenton, 6 miles from Sperryville and Warrenton. It is a good pike road all the way, and not subject to any interruptions, unless it be at Hedgeman's River. The ford may become impassable at any time, and the bridge we have just constructed, supported by piers and trestles, may be carried away by freshest. This is to be feared. A road leading form Gaines' Cross-Roads to Culpeper is the only route, east of Sperryville and west of the river, to that place. It is the old Richmond road, very bad, not traveled nor repaired for many years. It is hardly practicable for any force, unless cavalry, and small bodies at that, so it is reported to me.