Campaign for Petersburg

by Richard Wayne Lykes

This forward Union line was built on the crest of a ravine which had been crossed on June 18. Through this ravine, and between the sentry line and the main line, lay the roadbed of the Norfolk and Petersburg Railroad. The front in this sector was manned by Maj. Gen. Ambrose E. Burnside’s IX Corps. Among the many units which composed this corps was the 48th Regiment, Pennsylvania Veteran Volunteer Infantry. A large proportion of this regiment was made up of onetime coal miners, and it apparently occurred to one or more of them that Pegram’s Salient would provide an excellent place to use their civilian knowhow. Lt. Col. Henry Pleasants, the commanding officer of the 48th and a mining engineer by profession, overheard one of the enlisted men mutter, “We could blow that damned fort out of existence if we could run a mine shaft under it.” From this and similar remarks came the germ of the idea for a Union mine.

The 48th Regiment proposed to dig a long gallery from the bottom of the ravine behind their picket line to a point beneath the Confederate battery at Pegram’s Salient, blow up the position by powder placed in the end of the tunnel, and then send a strong body of troops through the gap created in the enemy’s line by the explosion. They saw as the reward for their effort the capitulation of Petersburg and, perhaps, the end of the war.

After obtaining the permission of Burnside and Grant, Pleasants and his men commenced digging their mine shaft on June 25. The lack of proper equipment made it necessary to improvise tools and apparatus with which to excavate. Mining picks were created by straightening army picks. Cracker boxes were converted into hand-barrows in which the dirt was removed from the end of the tunnel. A sawmill changed a bridge into timber necessary for shoring up the mine. Pleasants estimated the tunnel’s direction and depth by means of a theodolite sent him from Washington. The instrument, although outmoded, served its purpose well: the mine shaft hit exactly beneath the salient at which it was aimed.

Lt. Col. Henry Pleasants, onetime mining engineer and the commanding officer of the 48th Pennsylvania Regiment which dug the tunnel under the Confederate line.

Cross-section view of the Federal tunnel under the Confederate line. Colonel Pleasants later recalled that “General Burnside told me that General Meade and Major Duane, chief engineer of the Army of the Potomac, said the thing could not be done—that it was all clap-trap and nonsense; that such a length of mine had never been excavated in military operations, and could not be; that I would either get the men smothered, for want of air, or crushed by the falling of the earth; or the enemy would find it out and it would amount to nothing.”

Air tube Air-tight door Fireplace Chimney FEDERAL LINE Established June 18, 1864 Tunnel sloped up to avoid heavy clay Air tube JUNE 25, 1864, Tunnel started 510-8/10 feet JULY 27, 1864, 8,000 lbs. of powder placed here CONFEDERATE LINE JULY 30, 1864, Pegram’s Battery destroyed by explosion

One of the most remarkable features of the gallery was the method devised to supply the diggers at the end with fresh air. The longer the tunnel grew, the more serious the problem of ventilation became. It had been considered impossible to dig a tunnel for any considerable distance without spacing shafts at regular intervals in order to replace the polluted air with a fresh supply. This problem had been solved by the application of the simple physical principle that warm air rises. Behind the Union picket line and to the right of the mine gallery, although connected with it, the miners dug a ventilating chimney. Between the chimney and the mine entrance they erected an airtight canvas door. Through that door and along the floor of the gallery they laid a square wooden pipe. A fire was then built at the bottom of the ventilating shaft. As the fire warmed the air it went up the chimney. The draft thus created drew the bad air from the end of the tunnel where the men were digging. As this went out, fresh air was drawn in through the wooden pipe to replace it.

Work on the tunnel continued steadily from June 25, and by July 17 the diggers were nearly 511 feet from the entrance and directly beneath the battery in Pegram’s Salient. The Confederates had learned of the mine by this time and had dug several countermines behind their own lines in an effort to locate the Union gallery. Two were very close, being dug on either side of where the Pennsylvanians were at work. Although digging in the countermines continued throughout July, Confederate fears seemed to lessen during the same period. There were many reasons for this, one being the failure of their tunnels to strike any Union construction. Another major reason, undoubtedly, was a belief held by many that it was impossible to ventilate a shaft of any length over 400 feet without constructing air shafts along it, and so far no air shafts could be seen between the Union and Confederate lines.