A brother of Colonel Brownlow, who is now on a visit to this camp, informs me that he had it from the most reliable source, that the rebels in and around Knoxville were actually suffering for food. An order was issued by the rebel commander at Knoxville, a few days since, to seize all the hams, sides, and bacon belonging to private parties, leaving only fifty pounds for each family. A Mrs. Tillery, of Knox County, residing twelve miles from Knoxville, when her house was visited for the purpose of being pillaged, in the fulfillment of this order, expostulated with the lieutenant in command. She told him that fifty pounds would not keep her family two weeks, and she had no way of obtaining more. Notwithstanding her entreaties, the rebel lieutenant ordered fifty pounds to be weighed and given to her. He had scarcely given the order when Mrs. Tillery drew a pistol and shot the lieutenant through the heart. The rebel detail left the meat, and took off the corpse of their commander. The spirit of discontent is manifesting itself in various ways among even the most ultra rebels. They are getting tired of seeing their country devastated by the two armies, and are anxious for a settlement; and it only awaits the _daring of a few_ to inaugurate a "rebellion within a rebellion," which, if once started, will spread like wild-fire. PICKET DUTY AND ITS DANGERS. Of all the duties of a soldier, outpost duty is the most trying and dangerous. Courage, caution, patience, sleepless vigilance, and iron nerve are essential to its due performance. Upon the picket-guards of an army rests an immense responsibility. They are the eyes and ears of the encamped or embattled host. Hence, if they are negligent or faithless, the thousands dependent upon their zeal and watchfulness for safety, might almost as well be blind and deaf. The bravest army, under such circumstances, is liable, like a strong man in his sleep, to be pounced upon and discomfited by an inferior foe. For this reason the laws of war declare that the punishment of a soldier found sleeping on his post shall be death. But although the peril and responsibility involved in picket duty are so great, the heroes who are selected for it rarely receive honorable mention in our military bulletins. Their collisions with the enemy are "skirmishes." The proportion of killed and wounded in these collisions may be double or triple what it was at Magenta or Solferino, but still they are mere "affairs of outposts." "Our pickets were driven in," or "The enemy's pickets were put to flight," and that is the end of it. Presently comes the news of a brilliant Union victory; and nobody pauses to consider that if our pickets had been asleep, or faithless, or cowardly, a Union _defeat_ might, nay _must_, have been the consequence.