the presence of but few troops in the vicinity of Fredericksburg. They are to be found in small bodies and at long intervals along the shores of the Potomac. A prisoner sent to Washington yesterday informed me of about 1,800 stationed around Nomini Bay. My belief is that the great majority of the rebel force are encamped well in the advance, in anticipation of their inability to move promptly at this season of the year..

I have no changes to report in my immediate front..

Very respectfully, &c.,.

JOSEPH HOOKER,.

General, Commanding Division..

HEADQUARTERS HOOKER'S DIVISION,.

Camp Baker, Lower Potomac, Maryland, January 12, 1862.

Brigadier General S. WILLIAMS,.

Adjutant-General, Army of the Potomac:.

GENERAL: The Pensacola passed the batteries about 5 o'clock this morning unharmed. Fifteen or twenty shots were fired by the rebels as she descended the river, when she must have been lost sight of from that shore. From the Maryland shore an indefinable dark object was all that my pickets could see of her..

Later in the day the rebels were very active with their heavy guns, and blazed away at almost every object that presented itself, whether within the range of their guns or not. To me it seemed like an ebullition of anger or the escape of the Pensacola, for they had evidently made unusual preparation to receive here. Their ac- cumulation of ammunition was afterwards expended on objects of little or no importance and without result..

It is deserving of remark in the history of these heavy batteries, that during my sojourn here the enemy have discharged then not less than 5,000 times, and, with the exception of the single shot which s truck one of the vessels of the flotilla a few days since, while she was engaged in exchanging shots with them, not a vessel has been damaged in navigating the river nor the skin of a person broken on our shore.

I regret to learn that one of our barges was sunk two or three days since, off Alexandria, while on her way with stores for this camp. She is now at Rum Point. I am informed that she has on board stores from all of the departments, and I hope with care that no great loss will be suffered..

Very respectfully, your obedient servant,.

JOSEPH HOOKER,.

Brigadier-General, Commanding Division..

OFFICE OF CHIEF ENGINEER, ARMY OF THE POTOMAC,.

January 13, 1862.

General S. WILLIAMS, Assistant Adjutant-General:.

GENERAL: I deem it my imperative duty, after many representations to headquarters and to the chief of artillery on the subject of garrisoning the fortifications and preserving them from dilapidation, to call the attention of the Commanding General again to the subject, and to say that unless more effective measures are taken, these works, with their armament, must fall into ruin..