HALLTOWN, W. VA., August 25, 1864-11 p.m.

(Received 10.30 a.m. 26th.)

Major General C. C. AUGUR,

Commanding Department of Washington:

My reports from prisoners, scouts, &c., are such as to leave but little doubt in my mind that at least two divisions of Longstreet's corps, under the command of General Anderson, are here. I sent out two divisions of cavalry to make a reconnaissance to-day on the enemy's left flank; they met Breckinridge's corps on the march at or near Blue Spring or Leetown. Our cavalry skirmished sharply with this corps all afternoon, and were forced to fall back, all but one brigade coming into Halltown; this brigade (Custer's) is supposed to have crossed at Shepherdstown. The enemy now hold Shepherdstown. I cannot say whether they will cross or not; if they do, I shall try and strike them with their force separated by the river, which is reported to be rising. The reports are that Early marched with this intention this morning. I do not think they will move on Washington. Have you any news?

P. H. SHERIDAN,

Major-General.

ALEXANDRIA, VA., August 25, 1864-7.50 p.m.

Colonel TAYLOR,

Assistant Adjutant-General:

COLONEL: The patrols report all quiet to-day. It is reported that Mosby attacked the post at Falls Church about 1 o'clock last night, capturing two or three men and several horses.

H. H. WELLS,

Lieutenant-Colonel

HEADQUARTERS CAVALRY BRIGADE,
Near Fort Buffallo, Va., August 25, 1864.

Lieutenant Colonel J. H. TAYLOR,

Chief of Staff and Assistant Adjutant-General:

COLONEL: I have the honor to report that the party under Colonel Gansevoort returned early this morning. Colonel Gansevoort obtained positive information that there is no force at either Warrenton or Culpeper; that the Orange and Alexandria Railroad is used only as far as Culpeper; that squads of 50 and 100 men frequently come up on the railroad and pass through Culpeper on their way to join the main command in the Valley, and that a large force, consisting of over 10,000 infantry and cavalry, passed through Warrenton about a week since. This is probably the force of which you have already been informed. The usual small parties of guerrillas were met with. The party captured and brought in five prisoners (two soldiers and three citizens), forty horses, one mule,horse equipments, and harness leather. A number of rebel uniforms were found in a house near Warrenton and burned. A picket-post, consisting of a corporal and three men (near this camp), of the Sixteenth New York Cavalry, was attacked at 2 a.m. to-day by a party of mounted rebels; four horses and two men were taken; one man badly wounded, and the corporal escaped. Augustus Klock, a citizen living near Falls Church, was arrested by Mosby yesterday near Vienna, and was released this morning. He states that