Seven Worlds to Conquer
by Edgar Rice Burroughs
Prologue from the pulp version ~ Probably written by the Argosy editors.

The tale of the pioneer flight of the giant Zeppelin O-220 has already been told. In the Log Book of Great Adventures, written deep in red, have been inscribed the perils and privations, the victories and defeats, of those gallant companions from this land of ours who braved the mysteries of Pellucidar.

Pellucidar—mocked by smug scientists who blind themselves to the proofs that our Earth is a hollow sphere, containing a habitable world within its interior! Pellucidar—scorned and derided by timid savants who fear to see beyond their own knotted brows, scoffing that here is no great opening at the frozen poles, that only two plus two makes four!

But there were men of broader vision, of deeper understanding, in that prize crew of the Zeppelin O-220; One was a tall man mighty shoulders who walked with a cat’s soft tread; as Lord Greystoke he was known in London, though the creatures of the tropic wild called him Tarzan of the Apes. A second was Jason Gridley, the American explorer who financed the expedition. And chief among the others who believed and dared recklessly was young Wilhelm von Horst—know as Bill to his classmates at Boston Tech—who was chief navigation assistant to Captain Zuppner. 

The blood of adventure ran strong in the veins of von Horst. From his Yankee mother—she was Prudence Snow of Plymouth—he inherited the uncomplaining hardihood and independence of those seafaring New Englanders who tamed the waves in crazy cockle-shells. From his handsome, swashbuckling father, attaché to the pre-war embassy at Washington, he inherited a proud name, a strong lithe body, a bulldog tenacity which had marked his career through European schools and his American college.

His blue eyes had gleamed as he sat in the observation cabin atop the great Zeppelin, signaling the course across the chaotic ice-fields of the North. Exaltation coursed in him as the mighty ship found the vast entrance into the bowels of the earth that science denied. He shouted aloud as his keen eyes picked out a glimpse of land ahead—solid land in a place where hidebound geographers insisted should be only polar floes and endless water.

With the others he watched the rim of the midnight sun disappear from view as the glow of Pellucidar’s central sun glimmered ahead. He watched the great stretch of barren land fall astern and a mighty forest appear beneath them. Here were wooded plains and slopes that spread on and on in the distance until the haze of eternity engulfed them. Von Horst had been among the leaders who scampered down the ladders when the huge ship finally wafted to a landing.

The lush grasses, the growing scent of Pellucidar…

Tarzan of the Apes was the first permitted to explore. He had disappeared in that tangle of giant greenery, and long hours passed without sight or sound of him. A frown of worry began to knot Jason Gridley’s forehead.

“We must search,” he decided. “Here is Muviro, headman of Greystoke’s Waziri warriors. These natives know jungle sign—they can trail him if anyone can. If someone would volunteer to accompany—“

Von Horst sprang forward, smiling as he saluted. “The pleasure is mine. I’d like nothing better…”

And so it was that two white men and ten black sons of Africa plunged into the strange unknown. A game trail led them to a large open area, scantily covered with brush. Here their hour of terror began, for they were caught up in a strange stampede of such creatures as the eye of civilized man had never seen. Great ox-like beasts and giant red deer, gigantic sloths and mastodon and mammoth — pursued by the fierce flesh-eating saber-tooths. Flight was the only chance of survival for the humans — but somewhere in the rush young von Horst, of all the party, disappeared.

Had he toppled beneath a crunching hoof? Was his crippled body prey to some slavering jaw? Jason Gridley could not tell though he searched to the utmost of his ability. Even Tarzan was baffled upon his return, for the trail was cold and dead by then.

“Von Horst was doubtless killed,” was the general verdict. “We must return—“

But Jason Gridley shook his head. “The rest of you go on,” he said. “I will remain in Pellucidar until I have solved the mystery.”