Organized at Trenton, N.J., and mustered in April 27, 1861. Left State for Annapolis, Md., May 3. Reported to General Butler May 5, then moved to Washington, D.C., arriving there May 6. Attached to Runyon's New Jersey Brigade, Defences of Washington, to June, 1861. 1st Brigade, Runyon's Reserve Division, McDowell's Army of Northeast Virginia, to July, 1861.

SERVICE.

Battle Report Filed By Lt. Frederick E. Prime, U.S. Corps of Engineers, mentioning the

4th Regiment, NJVI (3 months)

FOUR-MILE RUN, VA., August 1, 1861.

SIR: In compliance with your instructions, I have the honor to report as follows with respect to my duties on Sunday, the day of the battle:

Early in the morning I proceeded with Colonel Miles, to whose staff I was attached, to Centreville, leaving my tool wagon and detachment at the cross-roads in Centreville. The battery near the road from Fairfax Court-House having been examined by Colonel Miles, the pioneers of the Garibaldi Guard were directed to construct a [redoubt] with two embrasures, so as to sweep the old Braddock road, and resist any attempt to outflank us from the left, by Union Mills road or road from Gaines' Ford. The road being still obstructed by the other columns, by order of Colonel Miles I started Colonel Davies' brigade on the road to Blackburn's Ford, reaching that road by a short cut across the fields. I then returned to Colonel Miles, and examined some positions for intrenchments on the left of the Blackburn road. These positions having been chosen, I was directed to proceed towards Blackburn's Ford with my tools. Reaching Colonel Richardson's brigade, I was informed that Colonel Davies was in command. I proceeded to the extreme left of the line and reported to him. I shortly after returned to the center, where Captain Hunt's battery was stationed.

I was directed by Colonel Richardson to remain near the battery and keep watch on the movements of the enemy. Colonel Richardson proceeded to make an abatis to cover a road for infantry and artillery, which should connect with the left. This road was formed on the skirt of the wood by cutting down the trees necessary for the abatis. Considerable progress was made in a battery across the road with three embrasures. This had a log revetment for the interior slope, and some ten or twelve feet of dirt in front. Captain Hunt's battery having been ordered to the left, Lieutenant Greene's battery was advanced to replace it, two pieces being on the right of the road and two on the left. An excellent view could be obtained of the infantry, cavalry, and artillery, as they moved either towards or from the main battle-field, the road in many places passing over cleared ground.

One hundred and sixty skirmishers were directed to proceed by a ravine our left to feel the enemy. I proceeded with them. On approaching the road near Bull Run the enemy's skirmishers fired upon them and they fell back, the orders being that no engagement should be brought on. Shortly afterwards I was directed by Colonel Miles to send my men and implements to Centreville, and to return with him, in order to attend to the defenses of that point. Shortly before reaching Centreville I was directed by Colonel Miles to put Colonel Blenker's brigade in motion immediately for Warrenton Bridge. I did so, and on Colonel Miles' arrival at Centreville I received orders to accompany the brigade and make a stand at Warrenton Bridge, or, if circumstances rendered it necessary, to countermarch and take a defensive position at Centreville.

The road was now thronged with a mingled mass of footmen, mounted men, wagons, &c. Before reaching the head of the column I received from an officer of high rank intelligence that the Army was in full retreat. I requested him to send the battery at the rear of the column back to Centreville. As I reached each regiment I had them deployed to the right and left to cover the retreat, with instructions to fall back slowly to Centreville. Colonel Blenker, with his leading regiment deployed in line of battle and covered with a line of skirmishers, asked for authority to move forward, so as to check any advance of the enemy’s cavalry. Deeming my instructions sufficient, I gave the necessary order in Colonel Miles' name, and was glad to learn from Colonel Blenker next day that an advance of cavalry had been checked and some prisoners released. I then returned to Centreville for orders, and, finding Colonel Miles had been relieved of his command, reported to General McDowell. By his direction I proceeded towards the Union Mills to ascertain if there were any signs of the enemy in that direction. None <ar2_336> being found, I was, on my return, directed to post the Twenty-seventh Pennsylvania Regiment on the right of the Blackburn Ford road. On returning from the discharge of this portion of my duty I was unable to find general headquarters. I remained with Greene's battery until I was informed that the Army had been ordered to fall back to Fairfax Court-House and make a stand.

At 3.30 Monday morning I was at Fairfax Court-House with my wagon, ready to carry out such orders as I might receive. The troops continued to file through the town, and I ascertained from Colonel Blenker that new orders had been issued, directing the troops to fall back to their old positions on the south side of the Potomac. I started my wagon and detachment for the engineer depot at Fort Runyon, and, at Colonel Richardson's request, accompanied him and his rear guard of two Michigan regiments. These, I believe, were the last troops that left Fairfax Court-House, and covered the retreat as far as the cross-roads formed by the Alexandria turnpike and road through Arlington Mills. I shortly afterwards ordered an advance, reaching Alexandria about noon on Monday.

Before closing my report I wish to mention Sergeant Field and ten men from the Fourth New Jersey (three months') Volunteers, who accompanied my tool wagon and brought it back in safety, being the most of the time separated from me.

Respectfully submitted.

 FREDERICK E. PRIME,

First Lieutenant, Engineers.

 Maj. J. G. BARNARD,

Corps of Engineer's, Washington, D.C.