1. _Mine Explosion_ (July 30).--From a hidden ravine in front of Petersburg, a mine had been dug underneath a strong Confederate fort. Just at dawn, the blast of eight thousand pounds of powder was fired. Several cannon, the garrison of three hundred men, and huge masses of earth, were thrown high in air. The Federal guns opened fire at once along the entire line. An assaulting column rushed forward, but stopped in the crater produced by the explosion. The Confederates, rallying from their confusion, concentrated from every side and poured shot and shell upon the struggling mass of men huddled within the demolished fort. To retreat was only less dangerous than to stay, yet many of the soldiers jumped out of this slaughter-pen and ran headlong back to the Union lines. The Federals lost about four thousand men in this ill-starred affair. 2. _Attack upon the Weldon Railroad_ (August 18).--By threatening Richmond upon the north, Grant induced Lee to move troops to that city from Petersburg. The opportunity was at once seized, and the Weldon Railroad captured. Lee, aware of the great importance of that means of communication with the South, for several days made most desperate attempts for its recovery. They were, however, unsuccessful, and the Union lines were permanently advanced to this point. [Footnote: An attempt was made by Grant to take this road when he first swung south of Richmond, but he was repulsed with a loss of nearly four thousand men. That this event was not mentioned in the military report, and has not received a specific name, shows the enormous proportions the war had assumed, and how changed it was from the time when Big Bethel and Ball's Bluff were esteemed important battles.] EARLY'S RAID.--Hunter's retreat (p. 262) having laid open the Shenandoah Valley, Lee took advantage of it to threaten Washington, hoping thus to draw off Grant from the siege of Richmond. General Early, with twenty thousand men, accordingly hurried along this oft-traveled route. Defeating General Wallace at _Monocacy River_, he appeared before _Fort Stevens_, one of the defences of Washington (July 10). Had he rushed by forced marches, he might have captured the city; but he stopped a day. Reinforcements having now arrived, he was compelled to retreat, and, laden with booty, he rapidly recrossed the Potomac. Not being pursued, he returned, and sent a party of cavalry into Pennsylvania. They entered Chambersburg, and, on failing to obtain a ransom of $500,000, set fire to the village, and escaped safely back into the Shenandoah. [Illustration: RESCUE OF THE UNION FLEET IN THE RED RIVER (Note, p 265)] SHERIDAN'S CAMPAIGN--Sheridan was now put in command of all the troops in this region. He defeated Early at _Winchester_ and _Fisher's Hill_, and in a week destroyed half his army, and sent the rest "whirling up the valley of the Shenandoah."