Fortbbss Mon'roe, Sopt. 8. Tlio flag of trucc boat Cossaek arrivod frora Aiken's Landing this morning with over six hundred Federal soldiers, paroled. On September 6th tbere wcr sixty-two of Gen. Pope's officers taken to Richinond and placed n close confinement in tho Libby prison, also aboitf thirty soldiers. The Richinond Enquirtr, of the 6th contains the fo'.lowing: " Tho past few days have been occupied in the bur'ml of the dead on the plains of Manassas. Tha raovements of the armies beyond aro uuknown. Tho game of strategy being deenied cssential by both combatants, Mie oiie for preservation, the other for the c:pture of Washington. " A flag of trace was sent out a daj or two after tho last battle, by tho enemy, asking permission to bury their dead. It was granted. Soon after a negro regiment, armed with spades, 8ppeared, and, after perforrning their work, were very properly taken in charge by our own tioops, most of them being ruuaway contrabands."