While this state of uncertainty mystified the General-in-chief, as he sat at the centre of his converging lines of telegraphic wires, and paralyzed the movements of the Army of the Potomac, there began to be an unusual activity of the rebel forces on the several roads leading through the passes of the Blue Ridge, in the direction of Harper's Ferry and Winchester. It was on Friday, the 12th day of June, that the first indications were seen of the approach of the enemy in force. On that day a strong reconnoitring party from Winchester was sent out on the Strasburg road, under command of Colonel Shawl, of the 87th Pennsylvania Volunteer Infantry. This party consisted of Colonel Shawl's regiment of infantry, the 13th Pennsylvania Cavalry, and one section of Battery L, of the 5th regular artillery; and when its advance was within about two miles of Middletown, it encountered a superior force of cavalry drawn up in line of battle. By a well-concerted piece of strategy, the enemy was lured into pursuit until he fell into an ambush, and received the effective fire both of our artillery and infantry from a dense wood within one hundred yards of the road. Repulsed and pursued by our cavalry, the enemy retreated in confusion, and in this handsome little affair lost no less than fifty in killed and wounded, and thirty-seven prisoners. These prisoners all proved to be part of the rebel forces which had long been in the valley, and thus served to allay all apprehension of the approach of any part of Lee's army from that direction.