...ngton, Sept. 19th, says that on the night of the 18th the Confederates blew up the piers of the new bridge at Harper's Ferry. They also destroyed everything that was possible to be destroyed at Harper's Ferry and along the line of the Thad to Martinsburg, including the splendid bridge, known as the Pillar Bridge, at that point. This morning there remained only a small force of rebels on Bolivar Heights,...