... Clay Street, is now in flamessup-posed to be the work of an incendiary. Loss not likely to be heavy. Raining moderately. There is a rumor that Frederick's Hall, between this city and Fredericksburg , was taken to-day by a detachment of the enemy's cavalry, an hour after Gen. Lee passed on his way to the army. This is only rumor, however. A dispatch from Gen. Lee's Chief Commissary, receiv...