HEADQUARTERS CORPS OF OBSERVATION,
Poolsville, October 29, 1861.

As much time must elapse before complete reports can be obtained from the various commanders of regiments, I have the honor to submit the following preliminary report of the operations of my command on the 21st instant.

On the 20th instant, being advised from headquarters of the movement of General McCall to Dranesville and to make a demonstration to draw out the intentions of the enemy at Leesburg,* I proceeded at 1 p. m. to Edwards Ferry with Gorman's brigade, the Seventh Michigan Regiment of Volunteers, two troops of the Van Alen Cavalry, and the Putnam Rangers, sending at the same time to Harrison's Island and vicinity four companies of the Fifteenth Massachusetts Volunteers, under Colonel Devens, who had already one company on the island, and Colonel Lee, with a battalion of the Twentieth Massachusetts Volunteers, and to Conrad's Ferry a section of Vaughan's Rhode Island Battery, and the Tammany Regiment, under Colonel Cogswell. A section of Bunting's New York State Militia battery, under Lieutenant Bramhall, was at the time on duty at Conrad's Ferry, and Ricketts' battery already posted at Edwards Ferry, under Lieutenant Woodruff.

The movement of General McCall on the day previous seemed to have attracted the attention of the enemy, as just before my arrival at Edwards Ferry a regiment of infantry had appeared from the direction of Leesburg, and taken shelter behind a wooded hill near Goose Creek, about 1 3/4 miles from our position at the ferry.

I ordered General Gorman to display his forces in view of the enemy, which was done without inducing any movement on their part, and then ordered three flat-boats to be passed from the canal into the river, at the same time throwing shells and spherical-case shot into and beyond the wood where the enemy were concealed and into all cover from which fire could be opened on boats crossing the river, to produce an impression that a crossing was to be made.

Orders were also sent to Colonel Devens, at Harrison's Island, 3 1/2 to 4 miles up the river and nearly east of Leesburg, to detach Captain Philbrick, with 20 men, to cross from the island and explore by a path through the woods, little used, in the direction of Leesburg, to see if he could find anything concerning the enemy's position in that directions, but to retire and report on discovering any of the enemy.

The launching of the boats and shelling at Edwards Ferry caused the rapid retiring of the force which had been there, and I caused the embarkation of three boat loads of 35 men each from the First Minnesota Volunteers, who, under cover of the shelling, crossed and recrossed the river, the boats consuming in the passage four minutes, six minutes, and seven minutes, respectively. The spirit displayed by officers and men at the through of passing the river was most cheering, and satisfied me that they could be depended on for most gallant service whenever something more than a demonstration might be required of them.

As darkness came I ordered Gorman's brigade and the Seventh Michigan Volunteers back to their respective camps, but retained the Tammany Regiment, the companies of the Fifteenth Massachusetts Volunteers, and the artillery near Conrad's Ferry in their positions, awaiting the result of Captain Philbrick's scout, remaining with my staff at Edwards Ferry.

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* See inclosure A to report 1, p. 290.

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