The watching gallery of Entry hall 904 was carved directly into the living brow of a black hard speckled rock cliff, jutting out above the underwater deep pit like the beak of a stone-hard cormorant. Here, four hundred paces above the drowned floor of the Third Tier, the ancient builders had set three circular viewports into the outer wall, each port five paces across, glazed with triple-layered discs of clear muscovite mica four inches thick, held within flanged collars of salt-hardened bell bronze. The rivets securing the collars were as thick as a man’s wrist, cast from copper-tin alloy and hammered flush into countersunk sockets lined with sheets of pure lead.
Qiao Ming stood before the central viewport, his bare soles cold against the unpolished flat stone slabs. He had removed his oilskin coat, draping it over a bronze mooring bollard to let the stiffened fabric dry in the warm, rotten-egg draft rising from the upright air-flow chimney pipes. His grey linen tunic, stained with animal fat and black salt-rings across the ribs, hung loosely over his lean, sinewy frame. In his right hand he held his brass star-compass, its aiming sights resting against the smooth, cold surface of the mica. Through the dense stone-glass crystal, a faint chill seeped into the bronze casing of the instrument. It condensed the moisture of the room into tiny beads of dew that ran down the engraved degree scales like beads of sweat.
