crossed the Potomac by the Long Bridge, on the morning of the 24th instant, assuming the command of the troops on the Virginia side. The troops took position as follows:

On the right, the Sixty-ninth Regiment N. Y. S. M., with crossed the Potomac Aqueduct, was posted near the canal culvert. The other two regiments of that wing (the Twenty-eighth N. Y. S. M. and the Firth N. Y. S. M.) were thrown forward on the road to Leesburg, about two miles from the river. In the center, the Seventh N. Y. S. M. was placed at the head of the Long Bridge. The Twenty-fifth N. Y. S. M. was posted at the toll-gate and Vose's Hill, on the Columbia turnpike. Three regiments of the New Jersey Brigade, under Brigadier-General Runyon, together with the Twelfth N. Y. S. M., occupied the Alexandria road as far as Four-Mile Run; the pickets of the Twelfth extending as far as the point where the canal crosses the Alexandria road. The left wing, consisting of the Eleventh Regiment N. Y. Vols. and the First Regiment Michigan, occupied the city of Alexandria, supported by the U. S. steamer Pawnee.

Immediately after crossing the river, I proceeded to an inspection of the whole line, commencing on the right. I found the Sixty-ninth N. Y. S. M. halted in position, waiting for the arrival of the intrenching tools in order to commence the works of defense which had been projected by the U. S. Engineers. Thence, following up the Leesburg road, I found the Twenty-eighth and Fifth Regiments N. Y. S. M. about a mile and a half in advance of the Sixty-ninth. At this place I found that Lieutenant Tompkins, of the Second U. S. Cavalry, supported by two companies of infantry of the Twenty-eighth, had advanced up the Leesburg road towards the Loudoun and Hampshire Railroad. I pushed forward with my staff, and found him at the point where the Leesburg road crosses the railroad. He had just intercepted a passenger train of cars on its way to Alexandria, and Lieutenant Houston, of the U. S. Engineers, had destroyed the track in front and rear of the cars and had destroyed two bridges by fire. I examined the passengers, and after conversation with them and the examination of private papers voluntarily exhibited to me, I thought it proper, with one exception, to impose no further restraint upon them than to detain them there until 5 o'clock p. m. of that day. This I did in order to prevent their carrying information of our movements into the neighborhood. Among them was a sergeant of the Fairfax Rifles, whom I sent to General Mansfield at Washington. I took pains here, and everywhere else, in my intercourse with the citizens, to impress upon their minds that the object and intention of the presence of the United States troops were to insure good order, and to afford protection to their persons and property in the pursuit of their ordinary avocations, and I am happy to say that I have been met everywhere by most of the people with expressions of kindness and cordial welcome.

Returning thence, past the positions of the Twenty-eighth and Fifth Regiments, I examined the cross-roads in the neighborhood of Arlington. Finding the mansion vacated by the family, I stated to some of the servants left there that had the family remained I would have established a guard for their security from annoyance; but, in consequence of their absence, that I would, by occupying it myself, be responsible for the perfect care and security of the house and everything in and about it. I then returned, by the head of the Long Bridge, where the troops were now engaged in throwing up intrenchments, under the direction of Captain B. S. Alexander, of the U. S. Engineers.