Captain Flint, was stationed, for Captain Conger's support. At the same time a detachment of the Maryland cavalry was sent to Bristoe Station, which detachment, having left that place, arrived a Manassas Junction at 2 o'clock p. m. yesterday, when immediately the whole force at that place was attacked and driven back, with a loss of 2 officers (Lieutenant Patterson and Lieutenant Dorsey, First Maryland Cavalry) and 15 men. At 4 p. m., Captain Conger, coming from Catlett's Station toward Bristoe Station, with about 40 men, was attacked about 2 miles south of Bristoe's Station by a force of 125 rebel cavalry, which he routed, his force returning by way of Manassas Junction to this place. This morning I am sorry to report that I lost the service of Captain Conger, his horse, during the fight, becoming disabled, and his brother (First Lieutenant Conger, of the Third Virginia Cavalry) and 1 man of the company only being missing. Twelve of the enemy's saddles, at least, have been emptied. we captured 2 prisoners and 3 horses. It seems that the enemy advanced from Warrenton Junction, with a strong force, to reconnoiter our advanced position, sending 150 men to Manassas Junction, and 125 men to Bristoe Station, the whole force evidently returning to Warrenton Junction. I have further learned from refugees and other reliable sources that the enemy has a force of 2,000 cavalry, consisting of the Second North Carolina, Seventh and Twelfth Virginia, a small detachment of infantry, with some artillery, at Warrenton. The strength of the infantry force is given variously from one company to two regiments. No force but strong pickets at Warrenton Junction, Rappahannock Station, and Fredericksburg. No re-enforcements whatever have been sent lately from Winchester to Warrenton. The rebels have only been running two trains this week to Warrenton Junction and Warrenton. Our scouts are sent in different directions. Shall report when they return. It would be of the utmost importance to have a signal corps attached to this corps, or at least two or three signal officers.

F. SIGEL,

Major-General.

Major-General BANKS.

(Repeated by Banks to McClellan, 8.15 p. m.)

FAIRFAX COURT-HOUSE,

October 27, 1862.

Captain Dahlgren, of my staff, returned from an expedition to Catlett's Station. He found the pickets of the enemy on the other side of Cedar Run, small patrols only having been lately to Greenwich and Bristoe.

Captain Conger, of the Third Virginia Cavalry, was seriously wounded in the engagement last Friday, and lies in a farm-house near Bristoe Station. Lieutenant Conger and 2 privates were taken prisoners and sent to Culpeper. Captain Conger fought with his small force (of about 30 men) a very strong force of the enemy (about 200). The enemy had 1 captain killed and 2 captains wounded, besides having 7 or 8 privates killed and quite a number wounded.

F. SIGEL.

Generals BANKS and HEINTZELMAN.

(Repeated to McClellan, 11 a. m.)