Gen. Longstreet.
--A correspondent of the Lynchburg Republican writes from Manassas Junction that Brigadier General James Longstreet, a gallant soldier of the Mexican war; has been assigned the command of the 4th Brigade now stationed there, and lately commanded by Col. Terrett. He was the first man to plant the U. S. flag on the wall of Chepultepec, after Major Selden was shot down.