HEADQUARTERS THIRTEENTH NEW YORK CAVALRY, Near Falls church, Va., September 28, 1864.

SIR: I have the honor to state that the escort of 500 men under my command moved on the evening of the 24th of September through Centerville, and thence through Thoroughfare Gap, striking and following the line of the Manassas Gap Railroad through Rectortown to Piedmont. Near Piedmont the house of Joseph Blackwell was burned, as directed, together with the barns and extensive outhouses. A large quantity of ammunition, artillery harness, and equipments was destroyed, including a large quantity of pistols and carbines, which were concealed from search in the house, and whose destruction was only known by their reports. This evidently was Colonel Mosby's arsenal and headquarters, as was shown by some articles of clothing and equipments. Near this point, having heard the condition of the railroad beyond Piedmont, the engineer, to whose wishes, by order, I was subordinate, stated that he had sufficient information and desired to return as soon as possible in order to make his report. Having ascertained by moving in close proximity to Manassas Gap that there was no regular force, if any, in the gap, I pursued the enemy by a detachment a mile beyond Piedmont, an returned by the way of Middleburg and Aldie to this camp. The railroad was found to be in good repair, except the growth of grass on track to Piedmont; beyond it was ascertained to be torn up and in need of repair. Nothing of interest occurred en route, excepting frequent skirmishes with and charges on the enemy. I desire to mention Lieutenant Farrell, Sixteenth New York Cavalry, for his conduct in charge of the rear guard near Rectortown. There are conflicting reports regarding Colonel Mosby-some stating that he is dead; all that he is severely wounded and below Charlottesville, Va.

I am, very respectfully, your obedient servant,
H. S. GANSEVOORT,

Colonel Thirteenth New york Cavalry.

Lieutenant E. Y. LANSING,

Acting Assistant Adjutant-General, Cavalry Brigade.

HEADQUARTERS CAVALRY, Near Piedmont, Va., October 15, 1864-1 p. m.

GENERAL: I have the honor to state that the portion of the Sixteenth New York under my command, being two squadrons, moved, as ordered, at an early hour this morning, by way of Orleans to Whit Plains, to report to Colonel alright. This leaves the entire force under my command, for squadrons of my regiment, Thirteenth New York Cavalry. The movement last night, which resulted in the capture of Colonel Mosby's pieces, was engaged in by my regiment, two squadrons of the Sixteenth new York Cavalry, and two companies of the Fifth Pennsylvania Artillery. My surmise that this artillery was concealed in the long range of mountains called the Cobblers, was confirmed by a statement drawn from a prisoner, and it was determined to develop the orality. At 9 p. m. 14th instant the above force was moved very intricate roads to a point at the base of the mountains, where a sort of bivouac was surprised and nine members of the battery captured, including Babcock, late captain C. S. Army, in charge of the artillery. This determined but little the localities of the pieces,