Cokinth, Miss., July G." Hon. E. M. Sfanton, Sccrctary of War Official reportg re just received of a brilliant cavalry afluir near BooneviJle, Miss , on tlie lst. Col. Sberiden, of tbe Second Micliignn Cavalry, with two regiment, 728 men, were attackcd by parts of eiglit regiments of rebels, numbering 4,700, which he dispersed and drove back after seven liours of fightiug. Wo lost forty-one lulled, wounded and missing. Tlie rebels' Ijss must havo been great. They left sixty-five dead on the field.