Four miles above the core floor, the rift entered the sulfur water drops zone.
Historically, this had been the most lethal section of the Continental Rift. For thirty hundred years, toxic fiery vapors and white-hot rotten-egg steam from the lower drain tube had drifted upward, meeting the freezing mountain air from the surface and condensing into skin-burning sulfuric acid rain that dissolved rope, rusted through iron, and melted human lungs. Quarry records from the Third Dynasty recorded that three out of every ten slave teams sent into the upper shaft died of lung hemorrhaging before reaching the two-mile mark. The old iron rungs driven into the stone by ancient royal survey squads hung in brittle, rusted festoons, eaten away by hundreds of years of chemical vapor.
Lin Tao paused on a narrow foothold of red sandstone. He wiped his brow with the back of his linen-wrapped wrist.
The skin-burning acid rain was gone. Instead of yellow, choking vapors, a thick, cool mountain fog drifted down from the upper rim, pearling against the rock face in drops of pure, drinkable water drops. The morning breeze carried the clear scents of the surface world. Crushed pine needles, damp wild sage, and rich, loamy earth warmed by early spring sunshine. The upright sandstone was cool and slightly damp. But fully free of the greasy yellow chemical residue that had stained the lower reaches of the deep gap for thirty thousand years.
