NIAGABA AND TUB SARATOGA. In point of strength, speed snd finish, tbe public will soon discover that they are unequall ed, and In command of experienced end skillful <esmen, via : Captains GEORGE W. COUCH and A. L. KING. The Pursers are well known totbe community, vis : Messrs. WILLIAM O. and J. M. SMITH. Theae Steamers will leave Pier No. 11. North river. New York, alternately every WEDNESDAY jnd SATURDAY at 3 o'clock, P. M.