Book excerpt: Professor Challenger returns to test one of his theories by digging underground and poking the planet in this classic adventure story. In The Lost World, Professor Challenger and reporter Edward Malone found dinosaurs living in the Amazon. In The Poison Belt, they witnessed chaos as Earth passed through a cloud of poison gas. Now, with the help of Peerless Jones, an expert in Artesian boring, they seek to test the professor’s Echinus theory . . . Professor Challenger believes that Earth is a sentient being. Like the sea urchin, it is protected by an outer layer, unaware of what happens on its surface. Challenger wants to dig beneath Earth’s protective layer, its crust, and touch the creature inside to let it know humanity is here. But what the men find underground is quite surprising . . .