But during this grand all-day attack, by two of McDowell's divisions, directly aided by part of a third, upon the left of the Enemy's original Bull Run line of defense--which attack, while it has failed in its purpose, has also utterly upset and defeated the Enemy's purpose to carry out Beauregard's plan of attacking Centreville that same morning --what has the Left Wing of McDowell's Army been doing? Let us go back to Sunday morning, and ascertain: All the Army of McDowell, save his Left Wing--which, comprising the two brigades (Blenker's and Davies's) of Miles's Division, and Richardson's Brigade of Tyler's Division that fought the preliminary battle of Blackburn's Ford, is now under the command of Miles,--moved away from Centreville, down the Warrenton Pike, as we have seen, very early in the morning. Blenker remains with his brigade as a reserve, on the heights a little East of Centreville, to throw up intrenchments; which, however, he does not do, for lack of trenching implements. Richardson and Davies are to make a feint, at Blackburn's Ford, so as to draw the Enemy's troops there, while the heavy blow of McDowell's Right Wing and Centre falls upon the left flank and rear of the Enemy's Bull Run line. Richardson's Brigade is already down the ridge, in his old position at Blackburn's Ford, when Davies with his brigade reaches it, from Centreville, and, by virtue of seniority, takes command of the two brigades. Leaving Richardson's Brigade and Greene's Battery exactly on the battle-ground of the 18th July, Davies posts two regiments (the 18th and 32nd New York) of his own brigade, with Hunt's Battery, on the brow of a hill, in an open wheat field, some eighty yards to the South-Eastward of Richardson, distant some 1,500 yards from Longstreet's batteries on the Western side of Bull Run,--and commences a rapid fire, upon the Enemy's position at Blackburn's Ford, from both of the Union batteries. At 10 o'clock, there is a lull in this Union fire. The Artillery ammunition is running short. The demonstration, however, seems, thus far, to be successful--judging by the movement of Rebel troops toward Blackburn's Ford. The lull continues until 11 o'clock. At that time Miles arrives at his front, in a towering rage. On his way down the ridge, that morning, early, Davies had made a discovery. While passing a roadway, his guide had casually remarked: "There is a road that leads around to the Enemy's camp, direct." "Ah!" --said Davies--"and can they get through that road?" "Oh, yes," replied the guide. Davies had at once halted, and, after posting his 16th and 31st New York Regiments, with two guns of Hunt's Battery, near this road, at its junction with the ridge road running up to Centreville and Black burn's Ford, had proceeded, with the rest of his regiments and guns, to the position where Miles finds him.