The moment Miles rode back to Centreville, Davies ordered out his brigade pioneer corps, all sturdy lumbermen of the North, with orders to fell trees and block up the country road thus left exposed. For two hours these sturdy men swung their axes among the heavy timber, answering the distant roar of the battle-field with a wild, crashing music, that broke with a new and more startling expression of war through the familiar roll of cannon. With sharp, crashing groans, the great trees were hurled to the earth, locked their splintered and broken boughs across the road, and covered it with mangled foliage, forming a barricade one-fourth of a mile long, impassable as a thousand cactus hedges. The roar of cannon afar off, and the batteries belching iron close by, failed to drown the groaning rush of these forest monarchs; and when the near guns were silent for a little time, as often happened, the almost human shiver of a tree, in its last poise before it rushed downward with a wail in all its leaves and branches, conveyed an idea of death more thrilling than any noise that battle-field had to give. At twelve o’clock, just after the pioneers had returned to position, a body of the enemy came down this road from Bull Run, intending to march on Centreville and take Miles’ division in the rear. Clouds of red dust rising from the trees betrayed them just as they had discovered the barricade, and a storm of shell and shrapnel hastened their backward march. About this time the road on the other side of Bull Run was one cloud of flying dust. It was Johnston’s forces, a close line, going up to snatch victory from the brave army at Stone Bridge. The advance of these forces became visible at first in tiny curls of dust rising from the woods. Then it swelled into clouds, through which jaded horses and tired men seemed struggling onward in a continued stream. At this time the distant cannonading became louder and more continuous; the far-off woods rolled up vast volumes of smoke, and where the battle raged, a black canopy hung suspended in mid-air. How those brave men, chained to their post by inevitable military law, panted to plunge into that hot contest! The inaction forced upon them when a struggle of life and death was going on in the distance, was worse than torture. They suspected the character of those troops moving forward in the red cloud, and followed them with eager, burning eyes. But they soon had work of their own to do!