above Harper's Ferry, on the Maryland side of the river, and threatened that they would turn that position, gain the rear of my pickets, an capture a considerable portion of my command, consisting of two companies of the Thirteenth Massachusetts Regiment. This information reached me at 11 o'clock at night; and one hour after I proceeded from my camp at this place with three companies of riflemen (B, I, and L) of my regiment, a section of the New York Ninth Battery, with two rifled cannon, commanded by Lieutenant J. W. Martin. After a very rapid and, owing tot he extreme [heat] of the weather, fatiguing march of 12 miles I reached Harper's Ferry about daylight on the morning of the 14th. I found the rebels then engaged in making an attack upon the troops stationed above my command near Sharpsburg. Those troops made a handsome defense, and before I could proceed tot heir assistance the rebels retired, under pretense of having received orders to report at once at Manassas.

On the morning of the 15th I acquired considerable knowledge of the position of the enemy, and, desiring to assure myself more particularly with regard to their movements, I detailed scouting parties to such points as the rebels were said to be, to ascertain the truth. One of these parties, consisting of an officer (Lieutenant Brown), 1 sergeant, and 6 privates, all of the Thirteenth Massachusetts Regiment, mounted, by my direction pushed forward as far as Antietam Ford; this party, returning, while opposite Pritchard's Mill, were fired upon suddenly from the Virginia side of the river by a volley of about 50 muskets from a body of men perfectly concealed. One man of the party was instantly killed on the spot, and, owing ot a continuous fire kept [up] on form the position to which they had taken themselves to prevent further losses as the enemy deployed down the river.

About the same time a number of the enemy made their appearance on the apex brow of the Loundoun Heights, also on the road leading [time] a considerably number of them opened fire from the heights back of Harper's Ferry and from all parts of the railroad along the river up to Pritchard's Mill. The latter were deployed, well covered behind the embankment of the railroad and bushes, and secreted in houses, barns, and lime quarries.

I stationed Company L, under command of Captain Barr, of my regiment, upon that portion of the Baltimore and Ohio Railroad below the abutment of the bent bridge, in the direction of Sandy Hook, with instructions to clear the Loudoun Heights and the road at heir base, which they did, causing the enemy quickly to retire, leaving 5 or 6 killed and wounded on the ground. I stationed a company and a half of the Thirteenth Massachusetts Regiment, commanded by Major Gould, form the bridge upward ot the first lock on the canal, a distance of about 1 1\2 miles, to defend against attacks form the ton and surrounding heights. I also left one piece of artillery with Major Gould's detachment in such position as to sweep the several streets of Harper's Ferry. I placed Company B, Captain Warden, of my regiment, above the lock, where the right of Major Gould's command rested, and deployed it where the right of Major Gould's command rested, and deployed it along the river about 1 mile. This company rendered very efficient service by its good marks meant long range and seriously galled the enemy. I then advanced with one piece of artillery, commanded by Lieutenant Martin; half of Company I, Thirteenth Massachusetts Regiemtn, commanded by Captain Shriger; and Company I, commanded by Captain McDonough, Twenty-eighth Pennsylvania Volunteers. The