will procure beef from the inhabitants, paying for it at the market rates by orders on the Chief of the Commissary Department at general headquarters.

The troops should be at the places indicated to-night, and they must have two days' cooked rations in their haversacks.

By command of General McDowell:

JAMES B. FRY,

Assistant Adjutant-General.

HDQRS. DEPARTMENT NORTHEASTERN VIRGINIA,
Centreville, July 20, 1861.

COLONEL: Yesterday was occupied mainly by the engineers in reconnoitering the defenses of the enemy on Bull Run, at and above the crossing of the Warrenton turnpike. Bull Run, though not a wide stream, is only to be crossed at certain places, owing to its precipitous, rocky banks. The Warrenton road crosses it over a stone bridge, which is mined and defended by a battery placed behind an unusually heavy abatis, whilst the bank on our side is clear. The ford above is also protected.

The object of the reconnaissance was to find a point which might be bridged or forded, so as to turn these places where the enemy are prepared for us. Thus far these efforts, five of them, have not been successful, the enemy being in such force on this side of the run as to make it impossible to ascertain. I wished yesterday to make the reconnaissance in force, but deferred to the better judgment of others-to try and get it by observation and stealth. To-day I propose to drive in the enemy and get the information required. If it were needed, the experience of the 18th instant shows we cannot, with this description of force, attempt to carry batteries such as these now before us.

I shall go forward early to-day and force the enemy beyond Bull Run, so as to examine it more closely than we have been able to do. i am told they obtain their supply of water from this stream. If so, and we get possession of the right bank, we shall force them to leave the now strong position of Manassas.

I am somewhat embarrassed by the inability of the troops to take care enough of their rations to make them last the time they should, and by the expiration of the term of service of many of them. The Fourth Pennsylvania goes out to-day, and others succeed rapidly. I have made a request to the regiment to remain a few days longer, but do not hope for much success. In a few days I shall lose many thousands of the best of this force. Will it suit the views of the General and the Government that they shall be replaced by long-service regiments? The numbers may be replaced, but it will not be an equal force.

I learn from a person who represents himself as having just come from General Patterson that he has fallen back.

There are rumors that Johnston has joined Beauregard. Yesterday some volunteers burned a house on Centreville Hill, which must have been seen by all the troops at Manassas; but the most thorough investigations did not lead to any discovery of the authors of this additional outrage.

I remain, colonel, most respectfully, your obedient servant,

IRVIN MCDOWELL,

Brigadier-General.

Lieutenant Colonel E. D. TOWNSEND,

Assistant Adjutant-General, Headquarters of the Army.