On the evening of the 11th instant I received information from Lieutenant-Colonel Carver, Fourth Maine Volunteers, brigade field officer of the day, that there was a report that a large body of rebel cavalry had crossed into Maryland and was now trying to recross into Virginia. I immediately sent word to the reserve at Weedon's Ford, and to the pickets along the whole line, and instructed them to be on the abler, ordering them to rally to the nearest reserve, in case of an attack during the night. About 9 o'clock the Third and Fourth Maine Regiments passed me on their way to the mouth of the Monocacy.

Early on the morning of the 12th instant, I heard picket firing toward mouth of the Monocacy, and shortly afterward some sharp artillery firing, apparently about 5 miles off, in the direction of the Sugar Loaf Mountain. Of this latter fact I at once advised brigade headquarters, by note, sent by a mounted orderly. About 9 o'clock my sentinel, on lookout on the hill behind me, reported a large body of cavalry on his right, advancing toward us.

I immediately ascended the hill with my reserve (three companies), and took up a position to completely cover ford with our rifles, and sent my sergeant-major to collect the pickets of the company on my immediate left, and send them to join me. He was then to proceed down the town-path to the reserve at Weedon's Ford, and give Captain Moore my instructions to collect all the force on the left and come to my assistance. When I arrived at the top of the hill, the enemy were plainly to be seen, distant about 1 mile, apparently about 1,200 or 1,500 strong, and still coming on. Just at this time Lieutenant-Colonel Carver came galloping down the tow-path, and called up to me that the rebels were close behind him. I told him that they were in plain view from where I was, and asked him if he had any instructions. He inquired if I could hold the point. I replied that if he would send me up the remainder of the regiment I thought I could. He left me and rode down toward Conrad's Ferry, with, as I supposed, the intention of hurrying up Captain Moore.

The rebel force advanced to within about half a mile, halted, and remained in that position for some half an hour, sending small parties down toward the tow-path. In the mean time I had been joined by Company D, the company on my immediate left, making my force about 100 men. This company I ordered to skirmish over toward the enemy and try and ascertain if he had artillery. In about ten minutes they returned and reported two pieces. At this time I received a message from Captain Mootree that Lieutenant-Colonel Carver had ordered him to remain where he was, instead of joining me. Directly upon the return of my skirmishing party, the rebels opened fire upon my position with their artillery, and a body of cavalry commenced slowly moving around toward my rear, still making no attempt to cross.

Finding that I was not to be re-enforced, and that if I remained my small force must be cut off and captured without being able to do any good, I commenced slowly falling back over the hills and ravines, toward Weedon's Ford, keeping close to the canal. I arrived at the ford a few minutes before Colonel Carver reached there from Conrad's Ferry, with a small re-enforcement from our old camp, of about 70 men. Under his directions I consolidated them with my regiment (now together), and advanced again toward White's Ford, deployed as skirmishers, my left resting on the canal; but before reaching White's Ford the enemy had accomplished his purpose and effected his escape. I then joined the fortieth New York Volunteers, which regiment had followed us up, and marched to the month of the Monocacy. Had Lieutenant-Colonel.