Colonel Henry Pleasants, of the Forty-eighth Pennsylvania Veteran Volunteers, to General Potter, who submitted the proposal to me soon after our sitting down before this place. It met my hearty consent and support. It was commenced June 25, prosecuted with great zeal through a difficult soil [sometimes of the nature of quicksand, at others a heavy marl], and with no tools but the ordinary intrenching spade and pick. The main gallery was finished July 17, 522 feet in length. It was then found that the enemy were at work in immediate proximity, and its further prosecution was conducted with great caution. Lateral galleries 37 and 38 feet in length, running under and nearly parallel to the enemy's works, were completed July 23, and the mine was ready for the charge. This, by orders from the general commanding, was put it on the 27th. It consisted of about 8,000 pounds of powder. Great praise is due to Colonel Pleasants and the officers and men of his regiment for the patient labor cheerfully bestowed on a work which deserved and met complete success.

On the 26th of July, at the request of the commanding general, I submitted a plan of assault, which contemplated the placing of the colored division of this corps in the advance, that division not being wearied by long and arduous duties in the trenches, as were the other divisions. A certain formation of troops was also suggested. This plan was not adopted as to these two points, and the troops were put in in accordance with the orders of the commanding general.

I received orders from the general commanding to spring the mine at 3.30 a.m. The troops were in position at that hour, massed behind the portion of our line nearest the point to be reached. The fuse, however, failed to ignite at a point where it had been spliced, and delay occurred. It was reignited, and the mine sprung at 4.45 a.m. Immediately the leading brigade of the First Division [the Second], under Colonel Marshall, started for the charge. There was a delay of perhaps five minutes in removing the abatis. Clearing that, the brigade advanced rapidly to the fort that had been mined, now a crater of large proportions and an obstacle of great formidableness. Mounting a crest of at least 12 feet above the level of the ground, our men found before them a huge aperture of 150 feet in length by 60 in width, and 25 or 30 in depth, the sides of loose pulverized sand piled up precipitately, from which projected huge blocks of clay. To cross such an obstacle and preserve regimental organization was a sheer impossibility. The lines of the enemy on either side were not single, but involuted and complex, filled with pits, traverses, and bomb-proofs, forming a labyrinth as difficult of passage as the crater itself.

After the training of the previous six weeks it is not to be wondered at that the men should have sought shelter in these defenses. Their regimental organizations were broken, and the officers undertook to reform before advancing. One regiment, the Second Pennsylvania Heavy Artillery, advanced some 100 yards beyond the crater, but, not supported, fell back.

It is reported that the enemy on my left opposite the Fifth Corps, on the explosion of the mine, left their lines and ran to the rear. But few shots were fired from that direction on the head of my column; it was otherwise on the right. An infantry fire was opened at once from the enemy's line up to within 200 feet of the crater; and as soon as the guns could be brought to bear artillery was opened upon our columns from across the ravine on our immediate right and from several works at a distance in front of the extreme right of the old line of the Ninth Corps.