HEADQUARTERS ARMY OF THE POTOMAC, Manassas Junction, Va., July 7, 1861.

Brigadier General IRVIN McDOWELL,
Commanding U. S. Forces, Arlington, Va.:

SIR: The bearer, Colonel Thos. H. Taylor, is sent (with an escort of twelve men and an officer, under a flank of truce) as bearer of dispatches from the President of the Confederate States to the President of the United States. He is instructed by the former to deliver his dispatches in person to the latter, and to return with the answer. His escort will await his orders.

I remain, sir, very respectfully, your obedient servant.

G. T. BEAUREGARD,

Brigadier-General, Commanding.

FORT McHENRY, July 8, 1861.

Colonel E. D. TOWNSEND,

Assistant Adjutant-General.

Four men, parties to the seizure of the St. Nicholas, were arrested on board the Mary Washington this evening. The officers and sailors of the St. Nicholas on board the Mary Washington identified the prisoners. The leader had a commission as colonel of the Virginia army, dated July 1, and signed by Governor Letcher. He was secreted in a bureau when arrested. Captain Williams, who arrested him, identified him as a West Point student.

NANTH. P. BANKS.

HDQRS. DEPARTMENT NORTHEASTERN VIRGINIA, Arlington, July 9, 1861.

General McDowell presents his compliments to General Beauregard, and begs to inform him that the paper referred to in his note of the 7th was delivered to the General-in-Chief, and by him transmitted to the President. When an answer shall be received from the latter it will be duly forwarded. In the mean while Colonel Taylor is instructed by the General-in-Chief to return this morning.

HEADQUARTERS DEPARTMENT OF ANNAPOLIS, Fort McHenry, July 9, 1861.

Colonel E. D. TOWNSEND,
Assistant Adjutant-General, U. S. Army;

SIR: The general commanding directs me to report, for the information of the General-in-Chief, that, in accordance with instructions from your office of July 5, the First Maryland Regiment left its camp at Mount Clare Station, Baltimore, at 9.30 o'clock p. m., on the 7th instant, with orders "to take post and cover the Chesapeake and Ohio Canal between Dams Numbers 4 and 5, and as much below and above as practicable." The regiment was under the command of General Cooper, of the Maryland volunteers, and was sent by the Baltimore and Ohio Railroad to Frederick, Md., where it was to be furnished with wagon transportation.