I am unable to discover any signs of raft or boat preparation, and the only signs of the enemy on he bank are small pickets, while there are no signs of large camps except at Leesburg and on Goose Creek. Those two do not appear very extensive, say for one or two regiments each. With a long-rang rifle cannon I could strip up the entrenchments erected for the defense of Leesburg, and perhaps make them betray the power of their guns, if they have any in position, which I doubt.

Major Myer, signal officer, arrived at Poolesville this morning, and will make trials to-night between my left and General Banks' position.

I would respectfully request that General McCall's force at Big Falls may be instructed to throw out pickets, say 4 1/2 miles above that position, to met the pickets of the Thirty-fourth New York Volunteers.

Five negroes crossed the river yesterday, running away, as they say, from being sent to Manassas to work on the fortifications. I respectfully ask instructions as to the disposition to be made of them. They say there is no large camp opposite this place for 3 miles back.

Very respectfully, I am, major, your most obedient servant,

CHAS. P. STONE,

Brigadier-General, Commanding Corps of Observation.

HEADQUARTERS ARMY OF THE POTOMAC,
Washington, D. C., August 23, 1861.

Brigadier General CHARLES P. STONE, Commanding Brigade:

GENERAL: Major-General McClellan directs me to inform you that it is a very well authenticated fact that the enemy are suffering severely with the small-pox, measles, and camp fevers. They have fallen back from Vienna to Flint Hill, taking all their sick with them. They moved even those who were so very sick that one or more died on the march. the pickets have been drawn back throughout the whole length of the line. They will probably change their plan of operation, as they see that we had divined their original plans and had mad preparations to frustrate them. This is written simply to keep you posted. The general does not wish you to be the less watchful because appearances indicate a retrograde movement on the part of the enemy.

I am, sir, very respectfully, your obedient servant,

A. V. COLBURN,

Assistant Adjutant-General.

OFFICE CHIEF OF ARTILLERY, ARMY OF THE POTOMAC,

Washington, August 23, 1861.

Major-General MCCLELLAN, Commanding Army of the Potomac:

GENERAL: In obedience to your directions I have the honor to submit the following.

To insure success, it is of vital importance that the Army of the Potomac should have na overwhelming force of field artillery. To render this artillery the most effective, the field batteries should as far as possible consist of regular troops. At present, of the twenty-five batteries of your army thirteen are regulars and twelve are volunteers. With every disposition to do their best, the volunteer artillery do not possess the knowledge or experience requisite for thoroughly efficient service. I would therefore recommend that companies of regular artillery be withdrawn from many of the forts of the Atlantic and Pacific