the Pennsylvania Brigade, was holding a by-road from Pine Grove to Cashtown . A cavalry scout, under Lieutenant Stanwood, was sent up Mountain Creek Valley, in the direction of the pass from Chambersburg to Gettysburg, through which it was supposed the enemy would send his trains, if he were defeated . Lieutenant Stanwood drove in the pickets a couple of miles from the turnpike, but had not sufficient force to press on . Captain Boyd joined me at Pen Grove, having followed the rear guard of the enemy to Fayetteville, on the Gettysburg and Chambersburg road, capturing prisoners . He was directed to pass by Bendersville, in the direction of Cashtown, to try and ascertain the movements and position of the enemy. He fell in with them, and captured eight wagons and -prisoners. During the day a small provision train came up, which was very acceptable, as it was impossible to subsist the troops from the country . A scout from General Meade also came through, giving the information the the enemy was retiring ; and latter in the day, Captain West, a volunteer aide and assistant on the Coast Survey, returned having successfully opened communications with General Meade on Saturday from Mount Holly. On Monday morning I marched the brigade by three different roads, concentrating at Newman's Pass behind Cashtown . We were, however too late intercept the trains which had gone that route . Tuesday morning, I was proposing to enter the Cumberland Valley and follow down the mountains toward Boonsborough, when an order came from General Meade to march to Gettysburg, which order was shortly after countermanded, with permission to do as I had proposed . The command was then marched to Altodale, and an officer sent to Chambersburg, to try and procure supplies, as my trains had failed to overtake me. A small supply being procured, the troops were marched on Wednesday to Waynesborough where I found General Neill, with a brigade of infantry and one of cavalry, and eight pieces of artillery . Here I was forced to wait for my trains to come up, but sent a cavalry scout to communicate with General Meade, west of South Mountain . Thursday was spent in waiting for rations to come up, and for instructions from General Meade. On Friday, I was ordered by him to occupy the enemy to the best advantage, and at be ready to join the Army of the Potomac or Genbarl Couch, as circumstances might require. Colonel McIntosh was at once ordered with his brigade of cavalry and four guns to feel the enemy along the Antietam below Leitesburg, which he did in the most skillful manner, driving his cavalry pickets across the creek upon their infantry and artillery supports. The cavalry was supported in this movement by tow regiments of Pennsylvania militia, under Colonel Frick, at Ringgold and Smithsburg, and one regiment, Forty-third New York Volunteers, from General Neill's command, posted near Leitesburg. On Saturday, hearing that rebels had ordered a miller on Marsh Run to grind wheat all night for them, Colonel Brisbane, with two regiments of Pennsylvania militia, was ordered, if possible, to intercept the wagons going for the flour, and destroy the grain if he could not bring it off. These regiments were supported by the Sixty-first Pennsylvania Volunteers, of General Neill's command . From 2 prisoners captured at the mill, we learned that the enemy had fallen back to Hagerstown. Colonel Brisbane's command was left at Waynesborough, with