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 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 had been coal miners, and it seemed to have occurred to one or more of them that Elliott’s Salient would provide an excellent place to use their civilian occupation. 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 the Union mine. This is what the 48th Regiment proposed to do: dig a long gallery from the bottom of the ravine behind their picket line to a point beneath the Confederate battery at Elliott’s Salient, blow up the position by means of powder placed in the end of the tunnel, and, finally, 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 constantly to improvise tools and apparatus with which to excavate. Mining picks were created from straightened 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 both direction and depth of the tunnel by means of a theodolite (old-fashioned even in 1864) sent him from Washington. The outmoded instrument served its purpose well, however; the mine shaft hit exactly beneath the salient at which it was aimed.