HDQRS. DEPARTMENT NORTHEASTERN VIRGINIA,
Fairfax Court-House, July 18, 1861.

SIR: The First Division, under General Tyler, is between Germantown and Centreville. The Second (Hunter's is at this place, just about to move forward to Centreville. The Fifth (Miles') is at the crossing of is ordered forward to Centreville by the old Braddock road; Barry's battery has joined it. One o Heintzelman's brigades (Willcox's) is at Fairfax Station. Heintzelman and his other brigade are below the station, but he has nor reported to me since we have been here, and I have not been able to communicate with him. I think they are at Sangster's Station. The four men wounded yesterday belong to Miles' Division, who had some slight skirmishes in reaching his position. Each column encountered about the same obstructions-trees felled across the road-but the axmen cleared them out in a few moments.

There were extra-sized breastworks thrown up at this place, and some of them with embrasures rivetted with sand bags. Extensive breast-works were also thrown up at the Fairfax Railroad Station and the road leading to Sangster's.

A great deal of wok had been done by them, and the number and size of their camps show they have been here in great force. Their retreat, therefore, must have a damaging effect upon them. They left in such haste that they did not draw in their pickets, who came into one of our camps, thinking,as it occupied the same place, it was their own. The obstructions to the railroad in the vicinity of the station, including the deep cut filled in with earth and tees, can be cleared out in a few hours. The telegraph poles are up, with the wires on them. i look to having communication by rail and telegraph in a very short time. Much flour, some arms, forage, tents, camp equipage were abandoned by them. I am distressed to have to report excesses by our troops. The excitement of the men found vent in burning and pillaging, which, however soon checked, distressed us all greatly. I go on to Centreville in a few moments.

Very respectfully, your obedient servant,

IRVIN MCDOWELL,

Brigadier-General, Commanding.

Lieutenant Colonel E. D. TOWNSEND,

Assistant Adjutant-General, Headquarters Army.

HDQRS. DEPARTMENT NORTHEASTERN VIRGINIA,
Centreville, July 19, 1861-12.30 a. m.

Brigadier-General TYLER,

Commanding First Division:

There seems to be a misunderstanding on your part of the order issued for a brigade of your division to be posted in observation on the road leading to the place where your command was engaged yesterday (July 18). It was intended that the movement should have been made long before this.

The train of subsistence came up long ago. I have given no order or instructions of a change int his matter.

I thought that the brigade was posted as desired until just now, when Major Brown, who is just returned from your headquarters, informs me that o action under these orders has been taken.