picks were made out of those used by our pioneers; plank I obtained, at first, by tearing down a rebel bridge, and afterward by sending to a saw-mill, five or six miles distant. The material excavated was carried out in hand barrows made out of cracker-boxes. The work progressed rapidly until the 2nd of July, when it reached an extremely wet ground; the timbers gave way and the gallery nearly closed, the roof and floor of the mine nearly meeting. Retimbered it and started again. From this point had to excavate a stratum of marl, whose consistency was like putty, and which caused our progress to be necessarily slow. To avoid this I started an incline plane, and in about 100 feet rose thirteen and a half feet perpendicularly.

On the 17th of July the main gallery was completed, being 510.8 feet in length. The enemy having obtained some knowledge of the mine, and having commenced searching for it, I was ordered to stop mining, which was, however, resumed on the 18th of July by starting the left lateral gallery.

At 6 p.m. July 18 commenced the right lateral gallery; but as the enemy could be heard very plainly working in the fort over us I caused this gallery to be excavated a little beyond and in rear of their work, and gave to it a curved line of direction. The left gallery, being thirty seven feet long, was stopped at midnight on Friday, July 22; the right gallery, being thirty-eight feet long, was stooped at 6 p.m. July 23. The mine could have been charged and exploded at this time. I employed the men, from that time, in draining, timbering, and placing in position eight magazines, four in each lateral gallery.

Having received the order to charge the mine on the 27th of July, I commenced putting in the powder at 4 p.m., and finished at 10 p.m.

The tamping was begun at 10 p.m. July 27, and completed at 6 p.m. July 28. Thirty-four feet of main gallery was tamped, and ten feet of the entrance of each of the side galleries; but the space between the magazines was left untamped.

I received orders from corps headquarters, on the 29th of July, to fire the mine at 3.30 a.m. July 30. I lighted the fuse at 3.15 a.m., and having waited till 4.15 a.m. an officer and sergeant of my regiment volunteered to go in and examine into the cause of the delay, and found that the fire had stopped where the fuses were spliced. They relighted it, and at sixteen minutes of 5 the powder exploded.

The charge consisted of 320 kegs of powder, each containing about twenty-five pounds. It was placed in eight magazines connected with each other by troughs half filled with powder. These troughs from the lateral galleries met at the inner end of the main one, and from this point I had three lines of fuses for a distance of ninety-eight feet. Not having fuses as long as required two pieces had to be spliced together to make the required length of each of the lines.

The mine was ventilated at first by having the fresh air go in along the main gallery as far as it was excavated, and to return charged with the gases generated by the breathing and exhalation of the workmen, by the burning of the candles, and by those liberated from the ground, along and in a square tube made of boards, and whose area was sixty inches. This tube led to a perpendicular shaft twenty-two feet high, out of which this vitiated air escaped. At the bottom of this shaft was placed a grating, in which a large fire was kept burning continually, which, by heating the air, rarefied it, and increased its current. Afterward I caused the fresh air to be let in the above-mentioned wooden tube to the end of the work, and the vitiated air to return by the gallery