General McDowell to push forward without delay to Centreville in pursuit of the retreating rebels, and the men, who were disappointed at having come so far to thrash their enemies without finding any, were eager to go on, but they were really exhausted by a long hot march over a dusty road, under a broiling sun, and prudence dictated that they should be allowed to rest, at least until evening. It is probable that they will go on either to-night or early in the morning, and continue this foot race towards Richmond a day's march further. Among the articles found and taken possession of at Fairfax was an unopened letter bag, well filled. It is not yet known whether it contained letters and correspondence to or from Fairfax. Its contents, when examined, will probably open a fresh mine of treasonable correspondence. There were also found a large number of army orders, company and regimental rolls and reports, showing the strength of the force stationed at that point. There are some curiosities among these prizes, and their being left behind is a strong evidence of the hurry in which the rebels abandoned the place. Your correspondent returned to the city this evening, bringing with him the brief official report of General McDowell to General Scott. No detailed report has been received from the left wing of the advancing column, but General McDowell's report includes all the casualties that have occurred in his whole command, and a general report has been received that nothing occurred in that branch of the column beyond the usual incidents of an advance upon a retreating enemy. It was stated at Fairfax Court House that the Alabamians, in considerable numbers, were intrenched upon the route of the divisions of Colonels Mills and Heintzelman. Early this morning the livery stables were besieged with applications for saddle horses and teams, by parties who desired to go into Virginia and witness the movement of the grand army, and if possible see a battle. Very few were gratified, as almost every thing in the shape of horse flesh worth having was previously engaged. A large number of civilians found their way along the almost blockaded road to the head of the centre advancing column, and kept with it until it halted within the breastworks vacated only an hour or two before by the rebels.
Operations of the right wing.
Vienna, Va., July 16, 1861.The long-expected order to move forward was telegraphed from Gen. McDowell's headquarters, at Arlington Heights, to all the division and brigade commanders of the grand army at two o'clock yesterday afternoon, and was communicated to the different corps during the brigade parades held in the course of the evening. The order was received by all the troops with the most enthusiastic demonstrations of satisfaction. The regimental commanders were instructed to hold their commands ready to move at 2 P. M., provided with cooked rations for three days. Accordingly the greatest activity prevailed this morning throughout the encampments, from the northernmost post, near the Chain Bridge, to the southernmost, near Alexandria. Tents were taken down and tied up, wagons loaded, arms put in order, ammunition dealt out, rations cooked, &c., &c. At noon everything was in readiness, and precisely at two o'clock the fifty thousand men, composing the grand army about entering upon the great work of sweeping secession out of the Old Dominion, were moving from their different positions towards their respective destinations. In accordance with my instructions, to follow the movements of the First division, under the command of Brigadier-General Tyler, of the Connecticut Brigade, I left General McDowell's Headquarters, at Arlington House, at the hour of march, for Fall's Church, for the last three weeks the Headquarters of General Tyler. Striking the road from Georgetown to Fairfax Court House near Fort Corcoran, I found it literally covered for a distance of over three miles with moving masses of infantry, cavalry and artillery, composing the four brigades of the First division. Passing Fall's Church, I soon came up with General Tyler and his staff, directly behind the advance guard. The three first brigades followed the Alexandria and Leesburg turnpike to a point two miles this side of Fall's Church, and then turned off to the left for this point — the fourth, under the command of Colonel Richardson, took a more direct route from their position near the Chain Bridge. The march was necessarily slow, the road being narrow and extremely broken, and the nearness of the enemy making it incumbent upon the advance guard to feel their way slowly and cautiously. As the twelve thousand men composing the three first brigades moved solidly and measur-edly on, they presented a most magnificent spectacle, when gazed upon from one of the many elevations overlooking the road. The seemingly endless forest of glittering bayonets, undulating with the ascents and descents of the road; the dark mass of humanity rolling on slowly but irresistibly, like a black stream forcing its way through a narrow channel; the waving banners, the inspiring strains of the numerous bands, the shouts and songs of the men, formed a most inspiring and animated scene, which was contemplated with both amazement and terror by the unprepared country people along the road. Some of these rustics manifested signs of gratification as the troops passed their several habitations. Others looked upon them with hostile sullenness, while again some made off for the woods as soon as they caught sight of the head of the army. When Colonel Keyes, riding at the head of