Introduction

Back to the Earth's Core is a Pellucidar story by William Gilmour, published in The Burroughs Bulletin #21, Spring 1971. It's relatively easy to find today, with copies appearing on eBay from time to time, and a digital version available at the Internet Archive.

The nineteen-page story features the author as narrator, and his friends and fellow Burroughs enthusiasts as principal characters. The action takes the men to the pendent moon of Pellucidar, here named Orbitar, and features a run-in with the horrible thorugs: tiny orangutan-like pygmy men who prey upon the native humans of Orbitar to eat their flesh. The gravity of Orbitar is slight during the daytime, and owing the the curious circumstances of its orbit and revolution, the gravity is nearly non-existent during the Orbitarian nighttime. The thorugs and native humans of Orbitar cannot move during the heavier daytime gravity, and only move about during the night. Our explorers from the earth's outer surface find themselves virtual supermen in comparison.

Besides the five principal characters, there are no other named characters. With only nineteen pages, there is no room for a princess or a romance, and there is no named villain. Gilmour does not introduce any native wildlife of Orbitar, and the only creature of Pellucidar that features in the tale is a thipdar (gigantic pteranodon.) The star of the story is the pendent moon itself, and the curious gravitational phenomenon that its unique position creates.

Chapter I: An Adventurous Prospect

William Gilmour, the narrator, pays a visit to the home of Vernell W. Coriell. Coriell is the founder of a literary society dedicated to the memory of Edgar Rice Burroughs--a society to which Gilmour belongs. Upon arriving, Gilmour finds Coriell in discussion with two other Burroughs aficionados: Stanleigh B. Vinson, the "possessor of the largest accumulation of Burroughs material capable of being conceived in the mind"; and Clarence "Bob" Hyde, whose collection rivals Vinson's.

The three are debating whether Burroughs's stories are fact or fiction. Hyde maintains they cannot possibly be true. Coriell and Vinson argue for their veracity. Gilmour agrees: the stories are true.

Bob Hyde scoffs. Burroughs may write with "profound realism" but it is preposterous to think that a world such as Pellucidar can exist. Coriell remarks that he's often wished to visit that inner world, and Vinson concurs. Gilmour suggests they contact his friend, the British inventor Jonathan Standish, who may be able to furnish a long-range helicopter with which they can enter Pellucidar through the North Polar opening. Hyde agrees to join the expedition, if only to see the others' faces when they realize they've been chasing a fantasy.

Gilmour telegrams Standish who immediately agrees to provide the helicopter and to accompany them on their expedition to Pellucidar.

Chapter II: Into Pellucidar

Gilmour, Coriell, Vinson, Hyde, and Standish search the Arctic region in Standish's enormous helicopter, the Bonnie Prince Charlie. After two weeks, Coriell spots the opening to Pellucidar, and Standish flies the Bonnie Prince Charlie through to the earth's core.

They land on the edge of a dense forest. The weather is warm so they remove their winter garments and dress appropriately for a safari. Standish suggests that as their food supply is low, they should hunt for meat. Hyde proves himself to be a crack shot and bags an antelope immediately.

After a meal of roasted meat, the men discuss the nature of Pellucidar and of the polar opening. Vinson puts forth a theory of gravity that he says accounts for the polar opening and for the inner world of Pellucidar. Then the men lie down in the Bonnie Prince Charlie for some much-needed sleep. Vinson takes the first watch.

Chapter III: Tragedy

Gilmour awakens feeling refreshed. Too refreshed. Vinson is missing, nobody is on watch, and everyone has slept round the clock. Gilmour wakes the others and they begin a search of the immediate area. They turn up Vinson's rifle but no trace of the man. There is no sign of a struggle and no tracks to show where he may have been taken.

They use the helicopter to search from the air, and find Vinson's pith helmet in a treetop nearly two miles away. Coriell surmises that Vinson has been carried off by a thipdar, an enormous flying creature that inhabits Pellucidar. By plotting a line from their camp to the tree in which they found Vinson's helmet, they determine the direction the thipdar took. They follow this line in the helicopter, hoping to catch up with the thipdar and rescue Vinson.

They follow the thipdar's presumed course to a high mountain range. They search the mountains for many sleeps, setting the helicopter down only to fish and hunt and eat. Eventually they are forced to admit there is nothing to find in the mountains, so they cross the range. Beyond is a vast fertile plain and beyond that, an ocean. To the right is an area of land that appears much darker than the surrounding terrain.

Suddenly, everyone falls to the ceiling of the Bonnie Prince Charlie.

Chapter IV: A New World

Standish wrestles with the helicopter to regain control. He plunges the craft into a power dive, pulling up and regaining control a mere fifty feet from the ground. He sets it down in a small glade.

The landscape is strange. The gravity is unusually low, and there is a definite horizon--something that should not exist in Pellucidar. The sun is no longer at zenith. Coriell surmises that they have landed on the satellite of Pellucidar. This small world orbits Pellucidar's sun at a distance of one mile from the surface of the ground. The satellite's orbital period matches the rotational period of the Earth, so the satellite appears stationary in relation to the surface of Pellucidar. The area of eternal shadow it casts on Pellucidar is known as Thuria, the Land of Awful Shadow.

Gilmour posits that during nighttime on the satellite world--when they are facing away from the sun and are closest to Pellucidar's surface--the gravitational pull of Pellucidar will act against the gravity of the satellite, rendering them nearly weightless. However, he's forced to admit he cannot explain why the satellite does not crash into the surface of Pellucidar.

Standish must make repairs to the Bonnie Prince Charlie, so he and Hyde stay with the helicopter while Gilmour and Coriell venture out to explore on foot. They cross a meadow and follow a ravine, noting the rocky formations and the complete lack of animal life. The ravine opens up onto a lush valley with streams, a large river, and a blue lake. Beyond the lake are a number of block buildings surrounded by a smooth stone wall.

Chapter V: Surprises

It's a city. It appears deserted, and Gilmour and Coriell decide to explore it. They make their way across the lake to the city. The city walls are smooth stone, ten feet high, with the only entrance being a heavy wooden door fastened tightly shut. Owing to the light gravity, Gilmour and Coriell leap over the walls. Inside the city walls, the square buildings are similarly constructed of smooth stone, with four-foot-tall wooden doors locked from the inside. There are no signs of life.

Coriell points to the sky. Due to the satellite world's rotation, the landscape of Pellucidar has become plainly visible overhead, a breathtaking vista.

The sun is rapidly setting. The two notice a large building with an enclosed paddock near the city center, and they move to investigate. Again taking advantage of the light gravity, they leap to the top of the paddock wall.

Around the paddock's edge are numerous stalls, and chained in many of the stalls are human beings. As they gape at the humans chained like dogs, a voice cries out a warning in English: "Go back! The sun has already set and they will be upon you at any moment!"

It is Stan Vinson.

Chapter VI: The Thorugs of Orbitar

Vinson implores the others to escape while they still can, and return to rescue him the next day. Coriell says no, they'll rescue him immediately. He uses his pistol to shoot through the cable that holds Vinson captive.

They turn to leave, but a horde of three-foot-tall orangutan-like ape-men rush into the enclosure and swarm the men. Gilmour uses his fists and Coriell fires his pistol, but Vinson grabs two of the creatures by the ankles and swings them around as flails. The others imitate his strategy and quickly clear enough space around them to permit them to make a flying leap for the walls.

They clear the walls--and then some! With the surface of the satellite now turned to face the ground of Pellucidar, the gravitational pull of Pellucidar works against the gravity of the satellite, considerably lessening the already-low gravity. The men's leap carries them far out over the city, and they discover that they can stay aloft--flying--by flapping their arms.

Still aloft, the men talk. Vinson recounts his adventures. He was snatched by a thipdar and carried to the vicinity of the satellite, where a second thipdar attacked the first. During the fight the thipdar released Vinson, and being caught in the satellite's gravitational field, he floated down gently to its surface. He passed out from exhaustion. When he awoke, he was a prisoner of the the tiny ape-men, chained beside other human prisoners.

During his captivity Vinson learned the language of the native humans of Orbitar, as the satellite world is called. The tiny ape-men, who are called Thorugs, eat the flesh of the native humans. The Thorugs, like all the native life on Orbitar, move about only at night when the gravity is lightest; the heavier daytime gravity renders them immobile.

Chapter VII: Back to Perdition

Night on Orbitar is relatively bright owing to reflected light from Pellucidar. Directly overhead the landscape of Thuria, the Land of Awful Shadow, is dimly but plainly visible. Encircling Thuria like a halo is the rest of Pellucidar, lit with the full glare of the sun.

Gilmour, Coriell, and Vinson do not return to the helicopter, but rather stay aloft all night while a Thorug horde follows them from below. When dawn nears, the Thorugs return to their city. Across the lake, a group of returning Thorugs drags two captives. Vinson thinks this must be a raiding party with two humans destined for the cooking pots.

Coriell suggests they return to the Thorug city during the day and free the captives. Vinson says that will be difficult: there are many prisoners, and--like the Thorugs--they cannot move during the high daytime gravity. At any rate, Standish and Hyde must be worried about their long absence, so they return to the Bonnie Prince Charlie.

Standish and Hyde are missing. At once all three realize: the Thorugs' captives were Standish and Hyde! The three return to the Thorug city, but Standish and Hyde are not in the paddock. Vinson questions an Orbitarian human captive, who struggles mightily against the gravity just to speak a few words. Hyde and Standish are being held inside the House of Orto, the large building next to the paddock. The door is locked from the inside. There is no way in!

Chapter VIII: Freedom

Gilmour returns to the Bonnie Prince Charlie and retrieves some dynamite, which he wires into two bombs. Coriell and Vinson help him plant the bombs onto two buildings in the Thorug city, then they wait for sunset. When night falls the Thorugs emerge. Gilmour has Vinson call out and tell them to release their two prisoners from the House of Orto, or face destruction. The Thorugs refuse--they do not believe the men can destroy the city.

Coriell fires the rifle into the hidden dynamite bomb, setting it off and blowing up an entire building. Shocked, some Thorugs bring Standish and Hyde out, while other Thorugs--unwilling to give up yet--struggle to pull them back inside the House of Orto. Vinson leaps into the melee, thrashes some Thorugs, and emerges with his comrades.

Then Gilmour has Vinson give the Thorugs another ultimatum: they must release all their human prisoners. Again the Thorugs refuse, but Coriell detonates the second bomb and the Thorugs rapidly set the prisoners free. The five men oversee the peaceful exodus of the former prisoners from the Thorug city. Vinson explains to the Thorugs that never again may they accost or raid the humans of Orbitar. They agree: never again.

The five return to the Bonnie Prince Charlie, which Standish repairs. Gilmour asks the others if they should return home. Vinson replies: "With all of Pellucidar still lying before us, you ask if we want to go home?"