Readers of the preceding volumes of this series will recall how the Pony Rider Boys came to spend their summer vacation on horseback, under the guardianship of Walter Perkins' tutor, Professor Zepplin. With a capable mountain guide, their first journey was through the wildest part of the Rocky Mountains, where they met with a series of rousing adventures and hair-breadth escapes—experiences calculated to try the stoutest hearts. It was here that the young explorers hunted big game—here that they discovered a valuable mine that had been the goal of prospectors for many years past.
All this was outlined in the first volume of the series, "THE PONY RIDER BOYS IN THE ROCKIES." In the second volume, "THE PONY RIDER BOYS IN TEXAS," was narrated how the four lads joined in a cattle drive across the plains of Texas, becoming real cowboys. Being by this time well hardened physically, they were able to do men's work in rounding up the stampeding cattle, which led them into many thrilling adventures. It will be recalled, too, how, during a visit to the mysterious church of San Miguel, the Pony Rider Boys solved the veiled riddle of the plains, which marked the end of the most eventful journey of their lives. In the third volume, "THE PONY RIDER BOYS IN MONTANA," we find the plucky lads following the old Custer trail over mountain and plain. It will be remembered how Tad Butler, while chasing a bear that had disturbed their camp, overheard a plot to stampede and slaughter the herd of sheep belonging to a rancher whom they knew; how the lad managed to escape from the men who sought his life; his eventual capture by the Blackfeet Indians, his escape, and the final solving of the mystery of the old Custer trail, during which the boys were in the thick of a battle between cowboys and sheep herders. In the volume preceding the present one the Pony Rider Boys were once more in the saddle in search of further adventure. In "THE PONY RIDER BOYS IN THE OZARKS," they met with a series of disasters and exciting experiences which tested their courage almost to the breaking point. They were beset by a band of robbers, who stole their ponies. Nearly all the party, one by one, was lost in the fastnesses of the Ozark wilderness. It will be recalled how the boys, during a visit to the Red Star Mine, were caught in a wreck far underground; how a car of dynamite exploded, making them prisoners in a rocky tomb, and how, after being rescued by a mountain girl, they discovered the real secret of the Ruby Mountain, narrowly escaping with their lives in doing so. No sooner had they brought this eventful trip to a close than they set out to face the perils of the great, silent desert of Nevada.
They were almost upon it now. Its spell was upon them and the lads fell silent as they waited anxiously for the first sight of the land which they had journeyed so far to gaze upon.
They had not long to wait after leaving the water hole where they had replenished their supply.
The guide at last rode out upon a rocky promontory, where he halted, waiting for the others of the party to come up with him.
"Where's the desert—is that it?" demanded Ned, riding up beside him.
The guide raised his hand in a sweeping gesture.
"The desert lies before you," he answered, his eyes traveling meditatively over the miles of waste and mottled landscape.
A brazen glare lay over the scene, while up from the white alkali flats rose a wave of heat that was suffocating. Old, dried-up water sinks lay white and glistening here and there, framed by vast areas of sage brush, while on beyond in the blue distance lay miles and miles of monotonous, billowing hills and mountains.
"Whew!" gasped Chunky, mopping the perspiration from his brow. "This is somewhat hotter than Chillicothe, Missouri. I wish I had a cake of ice to put under my hat."