...hattanooga, preparatory to crossing the river and retreating northward with all possible expedition. From the Upper Rappahannock there is much skirmishing, the usual preliminary to a battle; and Kemper 's brigade, of Pickett's division, went up thither last night, and it may be probable that a battle is imminent. Lee is apt to fight when the enemy is present facing him. The victory of Bragg has li...