point my command was employed on picket and scouting duty until July 29 (p. m.). I sent Lieutenant Jones and fifteen men to Greencastle, who picketed the roads below that place. My pickets extended from Shimpstown to McCoy's Ferry, Clear Spring, and Cherry Run. About 3 p. m. July 29 my pickets were driven in from McCoy's Ferry and Cherry Run to Clear Spring, from which place they were driven back within two miles of Shimpstown, when the enemy took a cross-road to the right leading to the Valley road, on which they advanced. I drew in my pickets from Shimpstown and sent a few men about one mile out on the Valley road, when they met the enemy's advance, and, after holding them in check for a short time, were driven back to the town, keeping up a sharp fire with them. I took my little command out of the town and formed line, but had hardly done so when the enemy charged through the town about 200 strong, driving my pickets before them. I held my position until they were within good range, and gave them a volley from my carbines, which checked them slightly. I then fell back on the Saint Thomas road. The enemy pursued me very rapidly. I checked them several times between Mercersburg and Bridgeport, when darkness coming on, and the enemy not being disposed to advance farther there, I left a picket near the town and went to Saint Thomas with the balance of my command, where I was joined by Lieutenant Stanwood, Third U. S. Cavalry. Soon after my arrival at Saint Thomas my picket at Bridgeport was driven in. I was compelled to fall back, keeping up a sharp fire with them until within about two miles of Chambersburg, where I was re-enforced by about forty infantry and one piece of artillery of the First New York Artillery, under command of Lieutenant Underhill. I sent some of the infantry to support my men, and held them until I placed the piece in position, when my rear guard, being pressed, fell back. I gave them a charge of canister, which checked them until I could get all the trains out of the town. I fired five shots from the piece, holding the enemy two hours, by which time I found I was being flanked, and drew my command into the town, passing through about 5 a. m. July 30. I fell back in order to cover the trains as far as Shippensburg, where I was joined by Lieutenant Jones, with the balance of my company, he having been compelled to fall back from General Averell's command. I remained at Shippensburg until July 31 (a. m.), when I took my command back to Chambersburg, remaining there until August 2 (p. m.), when I left Chambersburg for this post, arriving here August 3 (m.), having been absent eight days.

My loss is 2 men of the Permanent Company wounded; also 8 horses wounded. The officers and men all behaved very bravely. The enemy acknowledge the killing of 3 of their men and wounding 6 between Mercersburg and Chambersburg; also the killing of 1 and wounding of 4 men by a discharge of canister.

I would respectfully beg leave to mention Lieutenant Underhill, First New York Artillery, who, while directing the fire of his piece was subjected to a very sharp fire, acted with great coolness and handled his piece very well.

I am, major, very respectfully, your obedient servant,

H. T. McLEAN,

First Lieutenant, Sixth U. S. Cavalry.

Major W. B. ROYALL,

Fifth U. S. Cavalry, Commanding.