Thus admonished, Professor Wintergreen divested himself of his weapons, and, taking out a small notebook, began, with the compass before him, to make some calculations. At the end of ten minutes or so, he raised his head. "Well?" asked Jack eagerly. "Well," rejoined the professor, "it's not as bad as it might be. We are, according to my reckoning, about twenty-five miles farther to the south than we should be." He consulted his notebook once more. "The bearings of the mesa require us to travel in that direction." He indicated a point to the northward of where they were halted. "And it's twenty-five miles, you say?" asked Pete. "About that. It may be more, and again it may be less." "Waal, the less it is, ther better it'll suit yours truly. This stock is jes' about tuckered." With the professor now bearing the compass, they set out once more, this time taking the direction indicated by the man of science. "Suppose the professor is wrong?" Ralph whispered to Jack, as they urged their almost exhausted cayuses onward. Jack shrugged his shoulders. "What's the use of supposing?" he said. It was sun-down, and a welcome coolness had begun to be noticeable in the air, when Jack gave a shout and pointed directly ahead of them. "Look, look!" he cried. "What's that?" "That" was only a small purplish speck on the far horizon, but it broke the monotony of the sky-line sharply. Coyote Pete scrutinized it with keen eyes for a moment, narrowing his optics till they were mere slits. Then-- "Give me the glasses, perfusser," he requested. Every one in the party knew that their lives, or deaths probably, hung on the verdict of the next few seconds, but Pete's slow drawl was more pronounced and unperturbed than ever. He put the glasses to his eyes as unconcernedly as if he were searching for a bunch of estrays. Presently he lowered them. "Is--is it----?" began Jack, while the others all bent forward in their saddles, hanging on the rejoinder. "It is," declared Pete, and he might have said more, but the rest of his words were drowned in a ringing cheer. CHAPTER III. A NIGHT ALARM. "How far distant do you imagine it is?" inquired the professor, as they rode forward with their drooping spirits considerably revived. "Not more than fifteen miles--if it is that, 'cording ter my calcerlations," decided Pete. "Then we should arrive there by ten o'clock to-night." "About that time--yep. That is, if none of ther stock give out beforehand." "Why do they call it the Haunted Mesa?" inquired Jack. "Some fool old Injun notion 'bout ghosts er spirits hauntin' it," rejoined Pete. "Just as well for us they have that idea," said Walt. "They'll give it a wide berth." It flashed across Jack's mind at that moment to tell about the vague, gigantic shapes he had seen flit by in the gloom of the sand-storm. But, viewed in the present light, it seemed so absurd that the boy hesitated to do so.