than from fear as they gathered together their belongings, their furs and hides and crude stone implements; and the shambling man-shape, called Gor, led them to the hole down which a strong man might climb, led them down and still down....

But, as to the rest—Gor's promise of safe return to the light of day and that outer world where the Sun-god shone—how was Gor to know that a mighty glacier would lock the whole land in ice for endless years, and, retreating, leave their upper caves filled and buried under a valley heaped with granite rocks?

Even had the way been open to the land above, Gor himself could never have known when that ice-sheet left. For when that day came and once more the Sun-god drew steamy spirals from the drenched and thawing ground, Gor, deep down in the earth, had been dead for countless years. Only the remote descendants of that earlier tribe now lived in their subterranean home, though even with them there were some who spoke at times of those legends of another world which their ancestors had left.

And through the long centuries, while evolution worked its slow changes, they knew nothing of the vanishing ice, of the sun and the gushing waters, the grass and forests that came to cover the earth. Nor did their descendants, exploring interminable caves, learning to tame the internal fires, always evolving, always growing, have any remote conception of a people who sailed strange seas to find new lands and live and multiply and build up a country of sky-reaching cities and peaceful farmlands, of sunlit valleys and hills.

But always there were adventurous souls who made their way deeper and deeper into the earth; and among them in every generation was one named Gor who was taught the tribal legends and who led the adventurers on. But legends have a trick of changing, and instead of searching upward, it was through the deeper strata that they made their slow way in their search for a mystic god and the land of their fathers' fathers....

CHAPTER I

A Man Named Smith

eat! Heat of a white-hot sun only two hours old. Heat of blazing sands where shimmering, gassy waves made the sparse sagebrush seem about to burst into flames. Heat of a wind that might have come out of the fire-box of a Mogul on an upgrade pull.

A highway twisted among black masses of outcropping lava rock or tightened into a straightaway for miles across the desert that swept up to the mountain's base. The asphalt surface of the pavement was almost liquid; it clung stickily to the tires of a big car, letting go with a continuous, ripping sound.

Behind the wheel of the weatherbeaten, sunburned car, Dean Rawson squinted his eyes against the glare. His lean, tanned face was almost as brown as his hair. The sun had done its work there; it had set crinkly lines about the man's eyes of darker brown. But the deeper lines in that young face had been etched by responsibility; they made the man seem older than his twenty-three years, until the steady eyes, flashing into quick amusement, gave them the lie.

And now Rawson's lips twisted into a little grin at his own discomfort—but he knew the desert driver's trick.

"A hundred plus in the shade," he reasoned silently. "That's hot any way you take it. But taking it in the face at forty-five an hour is too much like looking into a Bessemer converter!"

He closed the windows of his old coupe to within an inch of the top, then opened the windshield a scant half inch. The blast that had been drawing the moisture from his body became a gently circulating current of hot air.

He had gone only another ten miles after these preparations for fast driving, when he eased the big weatherbeaten car to a stop.

n his right, reaching up to the cool heights under a cloudless blue sky, the gray peaks of the Sierras gave promise of relief from the furnace breath of the desert floor. There were even valleys of snow glistening whitely where the mountains held them high. A watcher, had there been one to observe in the empty land, might have understood another traveler's pausing to admire the serene majesty of those heights—but he would have wondered could he have seen Rawson's eyes turned in longing away from the mountains while he stared across the forbidding sands.

There were other mountains, lavender and gray, in the distance. And nearer by, a matter of twenty or thirty elusive miles through the dancing waves of hot air, were other barren slopes. Across the rolling sand-hills wheel marks, faint and wind-blown, led straight from the highway toward the parched peaks.

"Tonah Basin!" Rawson was thinking. "It's there inside these hills. It's hotter than this is by twenty degrees right this minute—but I wish I could see it. I'd like to have one more look before I face that hard-boiled bunch in the city!"

He looked at his watch and shook his head. "Not a chance," he admitted. "I'm due up in Erickson's office in five hours. I wonder if I've got a chance with them...."

ive hours of driving, and Rawson walked into the office of Erickson, Incorporated, with a steady step. Another hour, and his tanned face had gone a trifle pale; his lips were set grimly in a straight line that would not relax under the verdict he felt certain he was about to hear.

For an hour he had faced the steely-eyed man across the long table in the Directors Room—faced him and replied to questions from this man and the half-dozen others seated there. Skeptical questions, tricky questions; and now the man was speaking:

"Rawson, six months ago you laid your Tonah Basin plans before us—plans to get power from the center of the Earth, to utilize that energy, and to control the power situation in this whole Southwest. It looked like a wild gamble then, but we investigated. It still looks like a gamble."

"Yes," said Rawson, "it is a gamble. Did I ever call it anything else?"

"The Ehrmann oscillator," the man continued imperturbably, "invented in 1940, two years ago, solves the wireless transmission problem, but the success of your plan depends upon your own invention—upon your straight-line drills that you say will not wander off at a tangent when they get down a few miles. And more than that, it depends upon you.

"Even that does not damn the scheme; but, Rawson, there's only one factor we gamble on. No wild plans, no matter how many hundreds of millions they promise: no machines, no matter what they are designed to do, get a dollar of our backing. It's men we back with our money!"

Rawson's face was set to show no emotion, but within his mind were insistent, clamoring thoughts:

"Why can't he say it and get it over with? I've lost—what a hard-boiled bunch they are!—but he doesn't need to drag out the agony." But—but what was the man saying?

"Men, Rawson!" the emotionless voice continued. "And we've checked up on you from the time you took your nourishment out of a bottle; it's you we're backing. That's why we have organized the little company of Thermal Explorations, Limited. That's why we've put a million of hard coin into it. That's why we've put you in charge of operations."

He was extending a hand that Dean Rawson had to reach for blindly.

"I'd drill through to hell," Dean said and fought to keep his voice steady, "with backing like that!"

He allowed his emotion to express itself in a shaky laugh. "Perhaps I will at that," he added: "I'll certainly be heading in the right