...for Newbern, N. C.--The Richmond Dispatch of this date published a letter purporting to be from a nephew of Secretary Seward.--See Supplement. The combined rebel armies under Generals Bragg and E. Kirby Smith , reached Tennessee on their retreat from Kentucky this day. A correspondent, who accompanied the army, thus writes to the Sun, a rebel paper at Columbia, Tenn.: The combined armies of Generals Bragg ...