The high transverse arch was three paces wide and swept across the void with the tension of a drawn bow.
Up here, sixty arm-lengths above the deep gap floor, the air did not merely bite. It flayed. A thin, nonstop draft poured through the upper air-flow chimney pipes, smelling of dead nebulae and total zero. It was a wind without dust or moisture, so dry that when Qiao Ming blinked, his eyelids scraped against his corneas like dry thick parchment.
Yet he walked without pause along the crowned spine of the arch. His bare feet gripped the central ridge of the hard black rock pavers. There, the ancient stonecutters had chiseled shallow diamond hatchings to provide purchase for the draft-oxen of the First Flooding. The diamond ridges were coated in a glaze of glass-fused frost. But the hard, horn-like skin of his toes found the depressions between the cuts with unerring familiarity.
In his left hand, he held the Folded brass star-compass, its twin aiming sights unfolded and locked into position.
Every twelve paces, Qiao Ming stopped. He raised the heavy bronze instrument to his eye, aligning the rear pinhole with the front crosshair, sighting through the dark upper vaulting toward a series of faint, glowing studs embedded in the apex of the ceiling.
