NEW YORK,

September 19, 1863.

GENERAL: I have the honor to report that, on the evening of July 1, I resumed command of the Third Division of the First Corps, consisting of Rowley's and Dana's brigades. A third brigade of Vermont troops, under General Stannard, also reported to me about twilight of the same day. It consisted of the Twelfth, Thirteenth, Fourteenth, Fifteenth, and Sixteenth Regiments. The Twelfth and Fifteenth had been directed to act as a guard to the wagon train. The Fifteenth came up the next morning, but was again ordered back for the same line with them on the night of the 1st. They joined me the next morning, and were posted with my other brigades principally in reserve behind the western part of Cemetery Hill, to assist in the defense of that important position. On the 2d, the left wing of the Thirteenth Vermont Regiment, under Lieutenant-Colonel Munson, was ordered forward to support a battery, and a company of the Sixteenth Vermont was sent out as a support to the skirmishers in front. Toward twilight on the evening of the 2d, I received orders from the corps commander to form my men at once, and go to the assistance of Hancock's corps, which had been driven in by a desperate charge of the enemy. I marched my command as rapidly as possible to the place indicated, which was about a quarter of a mile west of the cemetery, and formed them on several lines by regiments for a charge. It was now discovered that the enemy had retired, and we were ordered to halt. My advance, however, consisting of five companies of the Thirteenth Vermont, under Colonel Randall, met Major-General Hancock, and asked permission of him to keep on and endeavor to rescue the guns of a regular battery, which had just been captured. The request was granted. Colonel Randall charged the retreating enemy in handsome style, retook the four guns that had just been lost, and also took two rebel guns, making six in all. My division bivouacked for the night on the ground occupied by us. The Sixteenth Vermont, under Colonel Veazey, was thrown out to the front on picket. The Vermonters, with the Twentieth New York and One hundred and fifty-first Pennsylvania Volunteers, held the front line during the remainder of the action, and the troops of Rowley's and Dana's brigades, with the exceptions I have named, held the second and third lines. About 2 p. m. a terrific artillery fire opened on us from more than 100 guns. The firing was accurate and incessant, and lasted for several hours, blowing up caissons from time to time, and sweeping away artillery and staff horses, as well as men, in every direction. I told the brigade commanders to shelter men and officers as much as possible, and, when the fire slackened, to be prepared to spring to their feet and meet the enemy with the bayonet, if necessary. Toward 5 o'clock I received notice from General Hancock and others that the final charge of the enemy had commenced. Shortly afterward several batteries and divisions from other corps reported to me as re-enforcement. I posted them, with the approbation of the corps commander, along the crest, at the points most threatened by the enemy's advance. With reference to this period of the action, I desire to quote the reports of General Stannard and Colonel Gates, of the Twentieth New