“There she is--there’s the Pass!” cried Sid triumphantly, as they topped the last of the awful sand ridges. His pointing finger showed them a river of desert vegetation below, a broad and rolling green river that flowed through the flat sandy plain of the Pass in masses of rich, living color. Tall green saguarros, like telegraph poles, rose in monumental spikes along the granite bases of the mountains on both sides. White fields of Bigelow’s choya barred their way, in big patches of them flung broadcast across the sands. Here and there the bright green puffball of a palo verde made a note of vivid color against the prevailing dark shiny green of the creosotes. At sight of all that verdure the horses broke into a run, twisting and threading through the flat bare sand lanes. The dogs, now desert-wise, galloped along beside them, barking excitedly and hardly noticing the choyas, avoiding them instinctively. And then Ruler gave tongue. _Ow-ow-ow!_ he sang, the first blessed musical notes of the chase that had come from his throat since they had left the Catalinas! Niltci whooped a shrill challenge and lashed his mustang to full speed. After him put out Big John, and then Scotty, glad of any excitement to take his mind off his troubles. Sid rode leisurely after them, merely glancing down at the tracks the dog had discovered in the sand. “Buck mule deer--a small one. Here, Blaze!--Heel!” he called sternly to the Airedale, who had started bounding after Ruler. Sid halted his horse and watched the three riders racing down the Pass. The frantic bellows of Ruler now told him that the deer had been sighted, and presently Sid got a distant glimpse of him, a tiny gray shape bouncing stiff-legged as he dodged through the desert cactus garden. “Mule deer all right! Guess we’ll stay out, Blazie,” he told the dog. “There are enough after him now to catch him with their bare hands! Let us try for mountain sheep, meanwhile.” He turned the pinto toward the base of the Hornaday Mountains which rose in rugged gray-green masses abruptly from the sand floor of the Pass. Their summits were ridged with rough pinnacles of gray granite. What might be on the other side of those ridges at once intrigued the exploring instincts in the boy. He was rather glad of this chance for a lone investigating hike--with good old Blaze his sole companion!