“They are deceived who flatter themselves that the ignorant and debased slave has no conception of the magnitude of his wrongs. They are deceived who imagine that he arises from his knees, with back lacerated and bleeding, cherishing only a spirit of meekness and forgiveness. A day may come—it will come, if his prayer is heard—a terrible day of vengeance when the master in his turn will cry in vain for mercy.”