"You promise never to betray me?" questioned the postboy, putting his hand up to the mail pouch, though not to remove it from its position on faithful Jack's back, but to be sure that it was securely in place. "We promise," declared the outlawed brothers in the same breath. "Away, Jack, old boy!" cried Little Snap, sharply, dealing his trained horse a smart blow with the flat of his hand. "On to Greenbrier!" Then, before the surprised twain could recover enough to prevent him, the gallant Jack leaped forward at the top of his speed, his body swaying to and fro, striking Buzzard Burrnock in such a way as to send him headlong down the abyss yawning on the right side of the road. Hawk Burrnock uttered a yell of dismay as he witnessed his brother's fate, and saw the horse dash onward down the descending way. "The fiends take——" He was raising his gun to fire at Little Snap as he spoke; but, in the midst of his speech and action, the intrepid postboy snatched his revolver from under his jacket, and, springing forward, dealt the outlaw a blow with its butt over the head that caused him to sink to the ground with a groan. "I didn't like to do it," said Little Snap, as he stood over the prostrate figure, "but he drove me to it. I do not think he is killed. He will soon come around all right. Wonder how Buzz Burrnock has fared," stepping at the same time to the edge of the bluff to look into the depths. A dark object caught in a thicket of bushes clinging to the side of the chasm twenty or thirty feet below soon resolved itself into the figure of a man. "He isn't as bad off as he might be," mused Little Snap. "Well, I will leave the precious pair to look after themselves." The clatter of a horse's hoofs in the Devil's Wash Bowl at that moment told that Jack had reached the foot of the descent and was beginning to climb the opposite heights. The postboy quickly placed his hand to his lips in such a way as to emit a short, sharp whistle, which rang up and down the valley with a peculiar clearness. CHAPTER II. THE MISSING MAIL. No sooner had Little Snap's shrill note rang on the air than the sound of the hoof strokes suddenly ceased, and a glad whinny answered him. "Noble Jack!" exclaimed the postboy; "I wouldn't give you for all the horses I ever knew, and I love them all. You are the best friend I have." "Quickening his pace, he descended into the huge basin denominated the Wash Bowl, meeting Jack, who was retracing his course at the bottom. "Good Jack!" said the young master, gently, while he patted the head of the faithful steed affectionately. "But we must tarry here no longer. On, my boy, to Greenbrier." Then Little Snap bounded lightly into the saddle, and, with a hasty glance backward, urged Jack away from the lonely place, half expecting to be attacked by some foe springing from behind the frowning rocks at every moment.