of the 5th instant I assumed command of Colonel McIntosh's brigade of cavalry, two pieces of light artillery accompanying it, Captain Martin's battery of rifled pieces, and my own brigade of infantry accompanying. I, in accordance with orders from headquarters Army of the Potomac, on the morning of the 6th pushed on from Fairfield to Waynesborough. The rear guard of the enemy only escaped capture by burning the bridge at the Antietam, 2 1/2 miles from Waynesborough, on the Hagerstown road. On the 7th, felt the enemy's pickets along the Antietam and Marsh Run, and found Ewell's corps in our front. On the 8th, discovered a portion of Ewell's corps at Middleburg. On the 9th, sent Colonel McIntosh, with the whole of his cavalry brigade and four pieces of artillery, to develop the strength of the enemy at the fords and bridges. Colonel McIntosh drew the fire of the enemy at the Antietam, and developed a force consisting of the three arms at Zeigler's Mills, near Chewsville, the pickets of the enemy being this side of the creek. Colonel McIntosh at once formed line of battle, dismounted his skirmishers, opened with his artillery, and drove them in full retreat across the Antietam, silencing their battery. He had 4 wounded, 1 mortally. This was between 3 and 4 miles from Hagerstown, on the north side. The enemy did not appear this side of the Antietam after this, in our direction. The cool and professional manner in which Colonel McIntosh handled his cavalry and posted his artillery has drawn upon him well-merited praise. In this as in every other duty which I called upon Colonel McIntosh to perform, his conduct and bearing impel me to suggest to the major-general commanding the Army of the Potomac that his rank should be increased so as to be proportionate to his gallant deeds and to his great ability. In connection with the advice and orders of General W. F. Smith, two regiments of militia, supported by one old regiment of my own brigade, were sent down to Marsh Run, to feel an infantry picket of the enemy. When we arrived there, we found the picket had been withdrawn the night before, and we did not get the militia under fire. On the 11th, marched to Leitersburg. On the 12th, made a flank march along the Antietam, and rejoined the Sixth Corps, in line of battle west of Funkstown. I may be permitted to state that all these events have lost their interest now by the more important developments which have since transpired, but, as the commander of the expedition which the major-general commanding saw fit to intrust to me, I have felt that it is but a simple act of justice to Colonel McIntosh to bear tribute to his gallantry and good judgment, and I believe he helped the enemy out of Hagerstown. Since joining the Sixth Corps, my brigade has been either in line of battle or marching, which is my apology for not having sent this report before. We have captured and picked up between 300 and 400 rebel prisoners or deserters. I sent them to Couch.

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

THOS, H. NEILL,

Brigadier-General, U. S. Volunteers.

General S. WILLIAMS,

Assistant Adjutant-General, Army of the Potomac.