FORTRESS MONROE, VA., March 26, [1863].

General BUSTEED, Yorktown:

Our troops at Williamsburg must defend themselves as long as they can and drive off assailants. We must not destroy towns unless they are actually taken possession of by the enemy, and then not unless absolutely necessary for our own safety.

JOHN A. DIX,

Major-General.

HEADQUARTERS THIRD NEW YORK CAVALRY,
New Berne, March 26, 1863.

Lieutenant Colonel SOUTHARD HOFFMAN,

Assistant Adjutant-General, Eighteenth Army Corps:

COLONEL: I have the honor to report that in obedience to the accompanying order I left New Berne yesterday morning at 7 o'clock and arrived at Mill Creek at 10.45 a. m.; finding the bridge entirely destroyed, I awaited the arrival of the pioneer corps; the bridge not being completed until night, we remained in bivouac on this side of the creek until 6 o'clock this morning, when I moved the column to McDaniel's plantation, 4 miles beyond Pollocksville; arriving at which place I dispatched a squadron and one howitzer under Major Fitz Simmons to Young's Cross-Roads and a like command under Captain pond to Trenton, giving each officer instructions in compliance with the order and verbal instructions from you. Between the hours of 11 and 12 the officers above named reported back to me, each reporting that there had been no vestige of Confederate troops in that vicinity for several days past. I immediately took up the line of march for New Berne, arriving here at 5 o'clock this evening.

It gives me pleasure to report that Lieutenant-Colonel McNary, in command of the One hundred and thirty-second and One hundred and fifty-eighth New York Volunteers, obeyed every request made by me.

I regret, colonel, my inability to perform the "big thing" you desired.

Very respectfully, your obedient servant,

G. W. LEWIS,

Lieutenant-Colonel, Third New York Cavalry.

[Inclosure.]

NEW BERNE, March 24, 1863.

Lieutenant-Colonel LEWIS,

Commanding Third New York Cavalry:

COLONEL: Information has been received that a pontoon train is en route for the White Oak River. You will therefore proceed with six companies cavalry and Allis' battery to-morrow a. m. to Pollocksville; gather all the information you can of any movements of this train; ascertain their purpose, if possible, and endeavor to intercept or catch them. Bring the train in, if practicable; if not, burn it.

You will necessarily use your own judgment in carrying out this movement. An infantry regiment will be sent toward and to Pollocksville.

The best way to take the train, if there be no evidence of tap, is the main object; the secondary one to ascertain what the object of the enemy is in sending the train to White Oak River.

By order of Brigadier-General Palmer:

SOUTHARD HOFFMAN,

Assistant Adjutant-General.