"Maybe I was mistaken after all," he thought to himself. "There was so much sand blowing at the time that I might very well have had a blurred vision." The next minute he was doubly glad that he had refrained from telling of his weird experience, for the professor, in a scornful voice, spoke up. "Such foolish superstitions did exist in the ancient days, when every bush held a spirit and every rock was supposed to be endowed with sentient life. Happily, nowadays, none but the very ignorant credit such things. By educated people they are laughed at." Pete, who was jogging steadily on ahead of the rest of them, made no rejoinder. Ralph, however, spoke up. "What would you do, if you were to see a spirit, professor?" he inquired, with an expression of great innocence in his round, plump face. "I'd take after it with a good thick stick," was the ready reply. "That is, always supposing that one _could_ see such a thing." Darkness fell rapidly. Night, in fact, rushed down on them as soon almost as the sun sank behind the western rim of the desert. To the south some jagged sierras grew purple and then black in the fading light. Fortunately there was a moon, though the luminary of night was in her last quarter. However, the silvery light added to the brilliance of the desert stars, gave them all the radiance they needed to pursue their way. The travelers could now perceive the outlines of the Haunted Mesa more clearly. It reared itself strangely out of the surrounding solitudes, almost as if it were the work of human hands, instead of the result of long-spent geological forces. "Wish we were there now," breathed Ralph, patting his pony's sweating forequarters, "poor old Petticoats is about 'all in.'" "It's purty hard to kill a cayuse," rejoined Pete. "I've seen 'em flourish on cottonwood leaves and alkali water--yep, and git fat on it, too. Be like a cayuse, my son, and adapt yourself to carcumstances." "Very good advice," said the professor approvingly, as the desert philosopher concluded. As Pete had conjectured, the ponies were far from being as tuckered out as they appeared, despite their sunken flanks and distended nostrils. As the cool night drew on, and they approached more nearly to the upraised form of the mesa, the little animals even began to prick their ears and whinny softly. The pack animals, too, seemed to pluck up spirits amazingly. "They smell grass and water," commented Pete, as he observed these signs. Shortly after ten, as had been surmised, they were among the bunch-grass surrounding the mesa. Striking such a spot after their long wanderings on the hot desert, was delightful, indeed. Presently, too, came to their ears the tinkling sound of flowing water. "It's the overflow from them old-timers' well at the base of the mesa," pronounced Pete, listening. "Yes, and here it is," cried Jack, who had been riding a short distance in advance, and had suddenly come across a small stream.