HEADQUARTERS FIRST CORPS, ARMY OF THE POTOMAC,
Centerville, Va., December 3, 1861.

Honorable J. P. BENJAMIN,

Secretary of War, Richmond, Va.:

SIR: I inclose you herewith for your information two communications from our agents, which would seem to indicate an early advance of the enemy, probably on this place and the battereies along the Potomac. Trusting in Providence, the sanctity of our cause, and the valor of our troops, we hope that victory will once more crown our efforts, whatever may be the odds the enemy will bring to bear against us. I beg to call your attention specially to that part of the communication from Alexandria which reads as follows: "Rumor states that we have a traitor in the War Department at Richmond who transmits news to Washington." We have lately received several communications to the same effect, and also (from other sources) that McClellan is fully informed as to the exact number of our forces here, which is only known to a few of our staff officers. Whether the reported rumor be true or not, I have thought it advisable to call your attention to t he subject in order to put you on your guard relative to the employes of the War Department who have access to its files.

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

G. T. BEAUREGARD,

General, Commanding.

[Inclosure Numbers 1.]

NOVEMBER 30, 1861.

SIR: The rumor current in Alexandria this day says there is an advance contemplated next week. Hundreds of wagons and large bodies of troops have been moved over from Washington within the last four days. Charles G. Addison, from Alexandria, will report himself to you as soon as he can reach Centerville. He, having left his home to-day, can tell you what preparation is being made for an advance.

Yours,

MARSHALL.

[Inclosure Numbers 2.]

ALEXANDRIA, November 30, 1861.

General BEAUREGARD:

DEAR SIR: I write to inform you what is going on around our city, hoping that it may prove of some service to you and our cause. On the 28th about 100 wagons came to town, also five regiments, and proceeded up the Leesburg pike. At 4 o'clock two regiments came in and went up on the railroad to Springfield Station. On the 29th eight regiments crossed over the bridge and went up the Columbia pike. I was in Washington yesterday and called at the War and Navy Departments, and from all I could see and hear they intend to make a forward movement. Sumner states that they will move at five different points to Leesburg, Fairfax, Occoquan, where the largest force will be thrown, and attempt to throw a force from Maryland across the river at or near the batteries-supposing that while they attack the forces at Occoquan you will draw your forces from them. This you must take as a rumor and use your judgment. From what I can see and hear they will be forced to try and do somehting desperate, as the Yankees are getting quite dissatisfied with General McClellan's inactivity. Rumor states that we have a traitor in the War Department at Richmond who trnasmits news to Washington. One regiment was sent over from Maryland