The plucky animal let himself out immediately and the admiring Alden still allowed the reins to lie on his neck. “You need no orders from me, old fellow,” said he; “when the history of the Pony Express is written, more credit should be given to you and your comrades than to some of the men who sat in the saddles.” The ridge which caused Alden anxiety had been crossed, and now when he looked back he traced the outlines of the vague column of smoke that was slow in dissolving in the summer air. Surely nothing more was to be feared from that source. No matter how well mounted a party of Indians might be, none could overhaul the peerless Dick, whose graceful legs were again doubling under him with marvelous rapidity and carrying him and his burden as an eagle bears its eaglet on its broad back. “Now, if I should have a flat sail on my right and left like a kite,” mused Alden, giving rein to his whimsical fancy, “this speed would lift us clear and we should skim through the air like a swallow. We should have to come down now and then, when the hoofs would give us another flip upward and away we should go. I’ll make the suggestion when I get the chance.” Suddenly he caught sight of a buck coursing in front. Where he came from he could not guess. Dick must have headed for him without either being aware of the fact, until the horse was almost upon the creature. The latter kept up his wild flight for several hundred yards when he was terrified to find that man and horse were gaining upon him. Then the buck showed a gleam of sense by bolting to the right. He made astonishing bounds and skimmed with arrowy speed, but it was less than that of his pursuer. Was there any creature of the plains which could surpass the half-bred mustang? No. Alden wondered whether the pony would change his course and press the pursuit of the game, as almost any one of his species would have done in similar circumstances. But Dick did not vary a hair until he confronted another pile of rocks. Instead of flanking them on the same side with the buck, he whisked in the other direction. What was a whole herd of deer to him? He carried the United States mail and everything must give way to that. From the moment that Alden saw the buck bounding in front of him, he could have brought him down without checking the pony. But he did not raise his rifle. To have fired would have been as wanton an act as the slaughter of the hundreds of thousands of buffaloes during the few years that followed. He was convinced that Dick was again going at the rate of twenty-five miles an hour. He would not have been surprised had the speed been even greater. That, however, was hardly possible. Again the still air rose to a gale and the velvety thumping of the delicate hoops was bewildering in its swiftness. He sat firmly in the saddle, leaning slightly forward and now and then jerking down his hat which was in danger of being whisked off by the wind.