Under these unpromising auspices, the army marched from the banks of the Potomac on the afternoon of July 16th. It advanced in four columns, toiling along under the burning sun and over the hot ground. One by the turnpike, one on the right, and one on the left of the railroad, and another between the turnpike and railroad. Expecting to encounter the enemy at Fairfax Court-House, seven miles this side of Centreville, where they had thrown up intrenchments, the three columns were directed to coöperate at that point. But the place was entered about noon on the 17th, only to find the intrenchments abandoned and signs of a hasty retreat visible. [Illustration: [Map]] [Illustration: [Map]] On the morning of the 18th, the different columns commenced their march from Fairfax to Centreville. While General McDowell made a personal reconnoissance to the left, making the forward movement a mere demonstration, Major J. G. Barnard, chief-engineer of the staff, proceeded to examine the enemy’s position in front. In this, however, he had been anticipated by General Tyler, who had pushed a brigade on towards Blackburn’s Ford. Troops were in motion on the plateau of Manassas, moving up to reinforce the enemy’s lines, and though no attack had been intended by the commanding general at that particular point, they opened upon them with two twenty-pounder guns in hope of ascertaining the position of these batteries. A reply was soon obtained—a battery, invisible except by the smoke, poured forth rapid discharges, and it required the assistance of a battery of rifled six-pounders to enable the Union troops to silence it. The brigade was then filed down to the stream and skirmishing maintained for some time. This battle, though apparently of small importance, was disastrous, inasmuch as it disorganized the arrangements of the commander-in-chief, and was accompanied by great loss of life, when compared with the magnitude of the undertaking and any beneficial result that could have sprung from it. The possibility of charging into Manassas, even under the most fortunate circumstances, was so remote, that the wisdom of an action at that point and at that time has been gravely questioned by the best military authorities. That night the columns of the army united, and encamped about a mile in the rear of Fairfax Court House, upon a broad hill-side, and on the extended plain at its base. A stream of water which crossed the grounds rendered the spot peculiarly important to the soldiers. The next day was spent in reconnoitering, and in determining how and where an attack should be made. The Stone Bridge was guarded by batteries, and the ground beyond obstructed by formidable abattis. The roads leading to fords between Blackburn’s and the Stone Bridge were mere by-paths, and the opposite bank of the stream steep, tangled, and obstructed. Two miles above, however, there was a good ford, but slightly guarded, at Sudley’s Spring.