At night Captain Robertson's brigade of horse artillery, temporarily attached, was ordered to join the command of Major-General Pleasonton. June 29. - Marched from Frederick City to about 1 mile beyond Brucevile. June 30. - Marched to Taneytown, and encamped a short distance beyond the village, on the Emmitsburg turnpike. On the evening of July 1, I was ordered to proceed to Gettysburg with about eight batteries and report to Major-General Hancock. I detailed the brigades of Captains Ransom and Fitzhugh, and, leaving about sundown, reported with them to General Gibbon, in the absence of General Hancock, at ebbed 10. 30 p. m. The same day, Lieutenant Sheldon, with his battery (B, First New York Artillery), was ordered to report to the chief of artillery of the Second Corps. I encamped that night on the Taneytown road, near the cross-road leading to Two Taverns. July 2. - In the morning I moved from camp with my brigades, and placed them in park behind the line of battle of the Third Corps, about 1 1/2 miles from Gettysburg. The remainder of the reserve batteries, having been ordered to join me, left Taneytown at early dawn, under command of Major McGilvery, and reported to me with the ammunition train about 10. 30 a. m. They were held in reserve on a cross-road between the main road and the Baltimore turnpike. Much to my regret, the two batteries of 4 1/2-inch guns (B and M, First Connecticut Artillery) were ordered to Westminster, to remain with the supply train. I am satisfied that the action of Gettysburg would have demonstrated their extreme mobility and usefulness as field guns, in addition to their already proved excellence as guns of position. Early in the day I stationed Captains Fitzhugh (K, First New York Artillery) and Rigby (A, First Maryland Artillery) and Lieutenant Parsons (A, First New Jersey Artillery) along the Baltimore turnpike at points designated by Generals Meade and Hunt. At 3. 30 p. m., pursuant to instructions received, I ordered Major McGilvery with two batteries (Fifteenth New York Battery and C and F, Pennsylvania artillery) of his brigade to report to Major-General Sickles. Afterward, as the action went on, I sent forward, as they were called for, the remaining batteries of that brigade, and in addition, those commanded by Captains Sterling (Second Connecticut Battery) and Ames (G, First New York Artillery), making in all six batteries of thirty-four guns. These Batteries were placed in position so as to fire upon the masses of the enemy moving up on our left flank, which made the general artillery line make a large angle to the infantry line of battle, and exposed it to a very galling enfilading fire of the enemy's artillery, in addition to the continual annoyance of their sharpshooters. These batteries, under Major McGilvery, held their places, doing terrible execution upon the successive columns attacking our left until about 6 p. m., when, our infantry falling back, they were compelled to retire, though contesting the ground gallantly under great disadvantages. Upon the crest of the hill, Major McGilvery formed a new line with the guns which he could collect, being re-enforced by Lieutenant Dow with his battery (Sixth Maine), and the farther advance of the enemy was checked by the fire of artillery almost unaided by infantry.