Gap. He was confronted by Sigel, whom he attacked immediately. Sigel was re-enforced by Heintzelman and Porter to-day. McDowell by noon was 4 miles from the field, and was merely waiting for his ammunition to come up to join him. The field of battle is near Gainesville. Sigel fought al day yesterday, slept on the enemy's ground, and this morning at 5 o'clock was attacked, and the cannonading was very heavy when a certain sutler, one of the parties who gives the information, left there. From all the evidence the inference is that we have met with no disaster and that Stonewall is in a tight place, unless he leaves to-night by Aldie. Jackson had with him yesterday three divisions - his own, Ewell's, and Hill's - amounting to 40,000 men. Birney held Centreville this morning and pursued Jackson, picking up many stragglers. The enemy left Centreville last evening. Many of the rebel dead are lying near Centreville. Birney ceased the pursuit on learning the force of the enemy. All of the best witnesses and all of the citizens who have passed consider Jackson in a dangerous position. Pope's train is parked this side of Centreville.

Truly, yours,

W. B. FRANKLIN,

Major-General, Commanding Sixth Corps.

P. S. - Pope is said to be very short of provisions, and the country will not support him.

GEO. B. McCLELLAN,

Major-General.

FALMOUTH, VA., August 29, 1862 - 8 p. m.

General H. W. HALLECK:

No attack has been med in front and none is anticipated in that direction. We have nothing to fear, unless from the right, should General Pope be overpowered, which I hope is not the case. The troops are well posted and all the have stores and baggage sent away, and in any event the place will be held as long as possible.

Since writing the above your dispatch, inclosing the one from General Pope, is received. Am glad to hear affairs are progressing so well.

A. E. BURNSIDE,

Major-General.

WASHINGTON, D. C., August 29, 1862.

Major-General POPE:

Trains will be started immediately to reconstruct bridges and carry out supplies. Yours of yesterday, 10 p. m., is the first I have received from your for four days. Live on the country as much as possible till we can supply you. Push the enemy as much as possible, but be sure to keep up your connection with Alexandria.

H. W. HALLECK,

General-in-Chief.

WASHINGTON, D. C., August 29, 1862 - 12.50 a. m.

General McCLELLAN, Alexandria:

It is reported to headquarters that Lee is advancing on Washington to-night, probably by the Chain Bridge. I doubt whether these works can be held with the raw troops. Can you not send a regiment there?

There is no artillery in Battery Martin Scott, nor any artillery at hand to sweep the bridge. I shall increase the force as much as the new troops at hand will permit. I would like your advice as to whether to hold the works or destroy the bridge. Can you not send a field battery?

J. G. BARNARD.