SIR: At 11 o'clock p. m. on the 25th of June last I received an order to report to Brigadier-General Stoneman at Major-General

Stoneman at Major-General Porter's headquarters. Arriving after midnight, I was directed to report to General Stoneman at his headquarters. Reporting, General Stoneman informed me that I was to accompany him on "an expedition to check Jackson's advance," having two regiments of cavalry, under Brigadier-General Emory, a light battery, and two regiments of infantry (the Seventeenth New York Volunteers and Eighteenth Massachusetts Volunteers, Colonel Barnes), and that the infantry would be under my command, as senior in rank. He ordered me to be at Old Church with the infantry as soon after daylight as possible. Getting my regiment immediately under arms, with ammunition and rations, I reached Old Church, via Cold Harbor, soon after 6 o'clock a. m. General Stoneman, with the cavalry and battery, arrived about 10 a. m. By his orders I moved the Seventeenth Regiment up to the junction of the road from Hanover and the turnpike to Richmond which crosses the Chickahominy at Mechanicsville. Here two sections of the battery were put in position, one having, one having been left at Old Church. I sent pioneers to destroy a bridge on the Hanover road.

Between 12 m. and 1 p. m. Colonel Barnes, with the Eighteenth Massachusetts, arrived by the Mechanicsville road, having taken a wrong direction, coming by the way of that village. The cavalry scouts brought frequent information of the enemy's cavalry being in our front. One report arriving with Colonel Barnes that a large force of cavalry was coming by Old Church, I sent Colonel Barnes there at once, when he took up position. The fight at Mechanicsville, the 26th of June, was distinctly heard, and as the enemy were evidently in the rear of our left, General Stoneman ordered me to fall back to the junction occupied by Colonel Barnes at Old Church, and just before dark a mile farther back on the Cold Harbor road, where we took up position for the night, having a ravine and small stream in our front, the bridge over the latter being destroyed. Toward morning a dispatch was received by General Stoneman from General Porter that " our troops had held their ground the 26th instant, but had fallen to a new line on Gaine's Mill and Cold Harbor, General Stoneman's command holding the extreme right."

The whole command was kept under arms, as they had been during the night. The battle of Gaine's Mill commenced, and we anxiously waited information. About 1 o'clock p. m. General Stoneman received an order from General Porter and one from General McClellan, directing him to fall back upon White House. The larger portion of the cavalry, under General Emory, started at once, the battery following, the Seventeenth New York flanking it on the right and the Eighteenth Massachusetts on the left of the road, followed by a rear guard of cavalry. As we started a large force of the enemy's cavalry was reported in sight of Old Church.

Our line of march was just in rear of the field of battle, the shells bursting within 800 yards of the road we were marching upon. The march was rapid and the day hot. Many men were left behind from partial sun-stroke, nearly all of whom came into camp before daylight.

We arrived at Tunstall's Station about 5 p. m. A section of the battery and four companies of the Eighteenth Massachusetts, under Major Hayes, took up position for the night at the bridge at the foot of the hill, about 1 mile below Tunstall's. Colonel Barnes with the balance