HDQRS. FIRST Brigadier, THIRD DIV., 16TH ARMY CORPS, Grand Ecore, La., April 13, 1864.

CAPTAIN: I have the honor to report the following relative to the part taken by my brigade in the battle of Pleasant Hill, La., on the 9th day of April, 1864: In accordance with orders received, we marched from Grand Ecore, La., on the morning of the 7th; after proceeding some 15 miles on the Shreveport road went into camp for the night. On the morning of the 8th, we were detained somewhat in waiting for the Second and Third Brigades to pass. We started at 8 a. m., and arrived near Pleasant Hill at dark, having marched 21 miles. During the afternoon heavy cannonading was heard in our front, denoting an engagement between our advance (the Thirteenth and Nineteenth Corps) and the enemy. At 2 a. m. of the 9th, we were under arms awaiting the approach of the enemy who had defeated the Thirteenth and Nineteenth Corps. Remained on our arms until 10 a. m., when we moved forward about 1 mile and formed in the following order in the east center of the field, viz: The Eighty-ninth Indiana Infantry in front, the Ninth Indiana Battery in its rear, and the Fifty-eighth and One hundred and nineteenth Illinois Infantry in rear of the battery. Remained in this position till 12 m., when the Fifty-eighth and One hundred and nineteenth Illinois Infantry were moved by the left flank to a point about 300 yards to the left and formed on a ridge in the woods, facing outward. From this point the Fifty-eighth Illinois was moved about half a mile to the front and left of the original position. Here this regiment was halted and a breast-work of fallen timber thrown up, behind which the men took shelter. After these arrangements were made skirmishers were thrown out from this regiment and the One hundred and nineteenth Illinois. The Eighty-ninth Indiana was then moved a short distance to the left, to support the Third Indiana Battery on the right and the First Vermont Battery on the left. The Ninth Indiana Battery was placed in position on the right of the Third Indiana Battery and about 200 yards therefrom, there being a New York regiment between. In this position we remained until 4 p. m., when musketry in our front admonished us that the fight had begun. Soon the enemy advanced from the woods, driving before them a brigade of Eastern troops which had occupied a position in the ravine or ditch on the opposite side of the field. Pursuing this brigade, and flushed with victory, the rebels continued to advance with yells that carried terror to many a stout heart. Still pressing on, they drove our troops back and even had possession of one of our batteries (Battery L, First U. S. Artillery), when on a sudden the Fifty-eighth Illinois Infantry, which had been advanced to the left and front, appeared in the edge of the woods on the enemy's right flank. The order was given to charge, and with unearthly yells and with lightning-like rapidity they were on the enemy. Fierce was the struggle, and nobly did the brave Fifty-eighth do their work. Driving the before victorious enemy before them, they halted not until the rebels were driven into the ditch in front. Here we captured about 400 prisoners, whom I sent to the rear in charge of an officer, with instructions to report them to Brigadier-General Mower, but who delivered them to a staff officer belonging, I have since understood, to the Nineteenth Army Corps. The Fifty-eighth Illinois claim to have captured more prisoners than they have men