...ward of victory. He says he will show no quarter to those taken in arms.--Phila. Bulletin, August 2. New Orleans papers state that a naval engagement took place this day at the mouth of the Mississippi River between the U. S. frigate Niagara and the little Confederate privateer J. O. Nixon; and that, after an action of twenty minutes, the Niagara crowded on every inch of canvas she could use, and made r...