Fourth Delaware and One hundred and sixty-eight New York Volunteers and the One hundred and sixty-ninth and One hundred and seventy-ninth Pennsylvania Drafted Militia, started from this post on the 4th instant, at 7 p. m., in the transport Winnisimet, and the gunboats Commodore Morris, Commodore Jones, and Smith Briggs, commander by Lieutenant-Commander Gillis, U. S. Navy. We arrived at Walkerton, on the Mattapony, about 3 a. m. on the 5th, and at 4. 30 marched for Aylett's, a small town on the Mattapony, 10 miles above Walkerton and 45 miles from the mouth of the stream. As there was a large force of rebels at the White House, 10 miles distant, I placed the detachment of the One hundred and sixty-eighth New York at the intersection of the road leading from the White House through King William Court-House with the main road to Dunkirk, and two detachments from the One hundred and sixty-ninth Pennsylvania Drafted Militia at the point where crossroads from the Court-House to the river lead to the main road. The rest of my command, having the Fourth Delaware in the advance, marched toward Aylett's, throwing out skirmishers, under Captain M. B. Gist, Fourth Delaware, to the front and on the flanks, the One hundred and seventy-ninth Pennsylvania Drafted Militia forming the reserve. We reached Aylett's about 7 a. m., when I halted my troops, having occupied all the approaches to the town and thrown out pickets. I found here a large iron foundry, where were molds for cannon and projectiles, and a number of shell and solid shot lying on the groans. This, with a large machine-shop, a lumber-yard, a store-house filled with agricultural implements, tobacco, cotton, turpentine, and other articles, and five Government houses, containing several thousand bushels of corn, were, in obedience to orders, destroyed. On the retreat, a very large grist-mill belonging to Colonel [W. R.] Aylett, of the rebel army, with eight "run of stone, " and containing 2, 500 barrels of flour and 2, 000 bushels of wheat, was burned. I also destroyed twenty barns and ten wheat stacks, containing in all 20, 000 bushels of grain; also some stores of bacon (about 2, 000 pounds), a quantity of tobacco, some cotton goods, and 80 gallons of whisky. I captured 120 horses and mules, and 80 head of horned cattle, all of which were driven to the wharf at Walkerton, but of which only a portion were shipped on board the transport, owing to the refusal of Captain Gillis to delay his return, he having received intelligence that the enemy were posting batteries along the banks of the river. I also report the capture of 2 rebel soldiers, who are now in the guard-house at Yorktown. One of these, from papers taken on his person, and which I have the honor to forward, I believe to have violated his parole. I ascertained that there was a force of 10, 000 rebels, under General [George E.] Pickett, at Newtown, 10 miles from Aylett's, and strong outposts within 3 miles of that place. Owing doubtless to the fact that my force was overestimated, we were not seriously attacked, although my rear guard, under Lieutenant Cullen, Fourth Delaware, skirmished with the enemy until within half a mile of Walkerton, which we reached about 5 p. m. As I had anticipated, the enemy endeavored to pass at the point occupied by the One hundred and sixty-eighth New York Volunteers, which repulsed him, with the loss of 1 man killed and 2 slightly wounded. In addition to this, I have to report the accidental wounding of Bugler [William H.] Dickerson. Com-