ALEXANDRIA, VA., August 27, 1862-11.60 a.m.

General HANCOCK,

General-in-Chief:

General Hancock informs me that he has heard for two hours past heavy cannonading in the direction of Centreville. There is nothing between here and there; I understand there is some cavalry here. The report of artillery has not been heard for the past half hour. Information from train conductor. The troops that left at 5 were taken to Union Mills and while unloading the fighting was heard 2 miles beyond. Both artillery and musketry were heard. An officer reported we had lost two batteries-eight guns. A portion of troops on the Bull Run-Bull Run being only half a mile from where the train was unloaded. Rapid discharges of artillery were heard, and fighting was on the left of the road.

JNO. J. KEY,

Major, Aide-de-Camp.

ALEXANDRIA, VA., August 27, 1862-12.14 p.m.

General HALLECK,

General-in-Chief:

At Bristoe, 4 miles beyond Manassas, four trains coming up. First train fired into succeeded in passing, but ran into the rear of another train at Union Mills and blocks the road. Second fired into was thrown off. The conductor escaped, and has just reported. All the trains taken, probably-two trains certainly. Three trains were attacked by infantry; conductor thinks eight companies at least. There were eight successive volleys. This occurred at 8 o'clock last evening.

JNO. J. KEY,

Major, Aide-de-Camp.

ALEXANDRIA DEPOT, VA., August 27, 1862.

General HALLECK,

General-in-Chief:

I ordered troop trains to proceed to Union Mills, 4 miles north of Manassas, where collision occurred, then march troops to Bull Run; leave 500 men to protect bridge, and balance, 2,500, to proceed to Manassas. The last of the troop trains had unloaded at Union Mills and returned to Fairfax Station, 6 miles. Report fighting 2 miles beyond Bull Run Bridge and cannonading in direction of Manassas. Further information as soon as received.

H. HAUPT.

FAIRFAX, VA., August 27, 1862.

Colonel HAUPT,

Alexandria, Va.:

I am convinced that we can do nothing at wreck without force to protect us. Rebels have a battery planted on hill and throw shell this side bridge. The railroad is lines with returning soldiers. One of our cavalry just in reports that rebel cavalry are in short distance of this place. I am not usually timid, but think there is no use of risking our two trains here to be captured. I await your order. I