The disposition and strength of Beauregard's forces at these various points along his line of defense on Bull Run stream, plainly shows his expectation of an attack on his right; but he is evidently suspicious that it may come upon his centre; for, as far back as July 8th, he had issued special orders to the effect that: "Should the Enemy march to the attack of Mitchell's Ford, via Centreville, the following movements will be made with celerity: "I. The Fourth Brigade will march from Blackburn's Ford to attack him on the flank and centre. "II. The Third Brigade will be thrown to the attack of his centre and rear toward Centreville. "III. The Second and Sixth Brigades united will also push forward and attack him in the rear by way of Centreville, protecting their own right flanks and rear from the direction of Fairfax Station and Court House. "IV. In the event of the defeat of the Enemy, the troops at Mitchell's Ford and Stone Bridge, especially the Cavalry and Artillery, will join in the pursuit, which will be conducted with vigor but unceasing prudence, and continued until he shall have been driven beyond the Potomac." And it is not without interest to note Beauregard's subsequent indorsement on the back of these Special Orders, that: "The plan of attack prescribed within would have been executed, with modifications affecting First and Fifth Brigades, to meet the attack upon Blackburn's Ford, but for the expected coming of General Johnston's command, which was known to be en route to join me on [Thursday] the 18th of July." The knowledge thus possessed on Thursday, the 18th, by Beauregard, that Johnston's Army is on its way to join him, is of infinite advantage to the former. On the other hand, the complete ignorance, at this time, of McDowell on this point,--and the further fact that he has been lulled into a feeling of security on the subject, by General Scott's emphatic assurance to him that "if Johnston joins Beauregard, he shall have Patterson on his heels"--is a great disadvantage to the Union general. Were McDowell now aware of the real Military situation, he would unquestionably make an immediate attack, with the object of crushing Beauregard before Johnston can effect a junction with him. It would then be a mere matter of detail for the armies of McDowell, McClellan, and Patterson, to bag Johnston, and bring the armed Rebellion to an inglorious and speedy end. But Providence--through the plottings of individuals within our own lines--wills it otherwise. Long before this, Patterson has been informed by General Winfield Scott of the proposed movement by McDowell upon Manassas,--and of its date.