About 8 o'clock Sunday evening, the brigade was ordered out to the position gained on the previous day, and instructed to hold it at all hazards. This was a task of no little difficulty and danger, as the nearest supports were half a mile away, and the rebel sharpshooters from the roofs of the neighboring houses and the tops of trees fired at every one who ventured to expose himself in the least to view. By selecting a good position behind a low ridge, and by throwing up a small breastwork, we were enabled to hold our position with the loss of but 1 man.

During the night the rebels were digging rifle-pits so near that we could hear their conversation, and once they charged upon us, as if to prevent us from shoveling, but a sharp fire soon convinced them that they would do better to let us work. At daylight every one was compelled to lie flat upon the ground, and remain in that position until dark. The rebels tried every means in their power to learn our strength, but in vain, as we were ordered to remain perfectly quiet, regardless of their conduct, unless they charged upon us. They exposed themselves to our view in large numbers, and tried to provoke us to fire by throwing bullets and shell at us very freely. At dark they began to approach us, and their skirmishers advanced on their hands and knees to within a few yards of our guards, but a volley from the rifles of two regiments satisfied them that they were going too far,and they retired. About 10 p.m. the brigade was relieved from their most wearisome and perilous duty,and ordered to return to camp across the river, where we arrived about 2 o'clock the next morning.

This being the eighth general engagement in which the Twenty-first Massachusetts Volunteers has acted an important part during the past year, it is superfluous to state that both officers and men behaved like veterans, and it is but just to add that the reputation won by the Second Brigade, under the gallant and lamented Reno, was worthily sustained at the battle of Fredericksburg.

I have the honor, captain, to be, very respectfully, your obedient servant,

W. S. CLARK,

Colonel Twenty-first Massachusetts Volunteers.

Captain G. H. McKIBBIN,

Assistant Adjutant-General, Second Brigade.

Numbers 125. Report of Captain Stephen H. Andrews, Thirty-fifth Massachusetts Infantry.

NEAR FREDERICKSBURG,

December 16, 1862.

SIR: I have the honor of reporting the action of the Thirty-fifth Massachusetts Infantry Regiment during the battle of the 13th, at Fredericksburg, which is most respectfully submitted.

At about 1 p.m. formed a line of battle, under command of Major Sidney Willard, and marched to the front at double-quick, facing heavy firing from the enemy's batteries and infantry.

Taking our position on the right of the Eleventh New Hampshire Regiment, we engaged the foe until our ammunition was exhausted; at which time gave way for re-enforcements to occupy our position, taking shelter under the brow of an elevation of the ground, where we remained until about 7 o'clock, when, on inquiry, we found the rest of our brigade.