Neither of them spoke again until they reached the spot where Buck had seen the car stop and the men get out and walk about. Here they dismounted and followed the footprints with careful scrutiny. Bud saw nothing significant, and when they had covered the ground thoroughly, he expressed his disappointment freely. Stratton merely shrugged his shoulders. "We'll follow the back track and see where else they stopped," he said curtly. His voice was a little hoarse, and there was an odd gleam in his eyes. When they were in the saddle again, he urged his horse forward at a speed which presently brought a protest from Jessup. "Yuh better take it easy, old man," he cautioned. "If that cayuse steps in a hole, you're apt to get a jolt that'll put you out of business." "I don't guess it'll hurt me," returned Stratton with preoccupied brevity. Bud gave a resigned shrug, and for ten minutes the silence remained unbroken. Then all at once Buck gave a muttered exclamation and pulled his horse up with a jerk. They were on the rim of a wide, shallow depression in the sand. There was nothing remarkable about it at first sight, save, perhaps, the total absence of desert vegetation for some distance all around. But Stratton slid hastily out of his saddle, flung the reins over Pete's head, and walked swiftly forward. Thrilled with a sudden excitement and suspense, Bud followed. "What is it?" he questioned eagerly, as Buck bent down to scoop up a handful of the trampled sand. "What have yuh--" He broke off abruptly as Stratton turned suddenly on him, eyes dilated and a spot of vivid color glowing on each cheek-bone. "Don't you see?" he demanded, thrusting his hand toward the boy. "Don't you understand?" Staring at the open palm, Jessup's eyes widened and his jaw dropped. "Good Lord!" he gasped. "You don't mean that it--it's--" He paused incredulously, and Buck nodded. "I'm sure of it," he stated crisply. CHAPTER XXIV THE SECRET OF NORTH PASTURE Jessup swallowed hard. "But--but--" he faltered, "there ain't never been any found around here. The nearest fields are hundreds of miles away, ain't they?" Stratton dropped the lump of sand. A number of particles still clung to his palm, and over the skin there spread an oily, slightly iridescent film. His manner had suddenly grown composed, though his eyes still shone with suppressed excitement. "Just the same, it's--oil!" he returned quietly. "There's no doubt at all about it. Look at the ground there." Mechanically Bud's glance shifted to the wide, shallow depression in the desert. The sand was noticeably darker, and here and there under the sun's rays, it held that faintly iridescent glint that was unmistakable. At a distance he would have said there was a spring somewhere beneath the surface. But no water ever had that look, and now that he was prepared for it he even noticed a faint, distinctive odor in the air. "By golly!" he cried excitedly. "You mean to say the whole pasture's full of it?"