HARRISONBURG, VA., September 28, 1864.

LIEUTENANT: I have the honor to submit the following report of the part taken by the Third Brigade, First Division, Army of West Virginia, in the action at Fisher's Hill, on the 22nd instant:

The Third Brigade (consisting of the Tenth Virginia, Major H. H. Withers; Eleventh West Virginia, Lieutenant Colonel Van H. Bukey; Fifteenth West Virginia, Major J. W. Holliday; Fifty-fourth Pennsylvania, Major E. D. Yutzy, and Twenty-third Illinois, Captain S. A. Simison) numbered on that occasion 1,465 officers and men for duty. The First Division on that day was formed left of the Second and the Third Brigade on the left of the First. The Second being absent, my position was thus on the left of our lines. The command being formed in two lines, the aggressive movement was initiated by a detour of two or three miles through woods and ravines to gain a position in the dense on the side of North Mountain, on the flank of the enemy's works, unobserved by him. Just before reaching the desired point a portion of our lines became exposed to his view in passing across a narrow strip of open ground, and was at once opened upon by his artillery with some effect. We were still moving by the flank, and pressed rapidly forward until our right rested clearly in rear of his works, when we came at once to a front and charged rapidly down the side of the mountain. The charge was made in gallant style, accompanied by deafening cheers and a rapid discharge of musketry at the onset. So sudden, unexpected, and demonstrative was this charge, and so fairly directed against the enemy's flank, that he was at once stricken with terror, and that portion of his infantry stationed on his left and near to us fled at the first discharge of arms and cheer from our men, and by their confused and rapid flight carried panic and conservation with them as they went. Our rapidly advancing lines became constantly more and more confused by the men of the rear line, who were possessed of the most physical strength, courage, and activity, pressing forward into the front line; the men of my command becoming thus mingled with those of the First Brigade (Colonel Wells), and finally the officers and men of this character throughout the entire command had the advance and quickly planted our flag and had possession of the guns on the left of the enemy's position; but without pausing or giving his time to rally or change his front, they continued to press forward in the manner above described taking position after position and capturing guns at each, until he was finally driven in confusion from the whole of his lone of works and completely routed, our pursuit only terminating with the coming of darkness, the charge having been made after 4 p. m., and our men having passed rapidly over hill and hollow, through woods and open ground for a distance of three or four miles. During the greater portion of this time I was engaged in urging forward the more timid and weak, and driving from cover the cowardly, that i might thus maintain a reserve for the support of the brave fellows who had gone forward, in the event of their being brought to a stand or meeting with a repulse. Consequently, I cannot speak from personal observation, except in general terms, of the valiant conduct of that portion of my command which was with our advance. I only know that the color-sergeant of the Tenth West Virginia claims to have been the first to plant our flag on the enemy's works, and that he seems to be well supported in this claim by his comrades who stood by his side, and that the Twenty-third Illinois and Eleventh West Virginia brought out each a battle-flag. Many also of my officers and men from the various regiments claim to have captured guns as they advanced.