The intake well of Sluice Gate Nine was a deep pit of churning green froth.
Qiao Ming hauled himself onto the narrow upkeep ledge that skirted the northern flank of the basin. The ledge was barely two spans wide, cut from dense grey red stone and slick with wet sea-glass speck grease that had piled up over thirty hundred years of salt-mist. Fifty arm-lengths below his iron cleats, the surface of the intake pool roared like an open blast fire. The water was not flowing smoothly into a discharge channel. It was piling upon itself in violent, swaying surges that threw sheets of cold spray thirty feet into the darkness of the vault.
He wiped the bitter salt water from his eyelids and brought his lantern forward, sheltering the animal fat flame beneath his leather apron.
Before him rose the massive stonework of Sluice Gate Nine.
Forged during the First Epoch from deep-sea glowing-bronze and cold-cooled star-fallen iron, the gate was forty arm-lengths wide and eighty arm-lengths high from doorstep to stone beam. It weighed forty tons, suspended within a giant stone frame of dressed granite blocks fastened with lead-poured iron cramps. Two linked balance weight chains, each link forged from black bronze as thick as a bull’s neck, rose from the gate’s upper lifting eyes to disappear into the ceiling pulley wheels eighty arm-lengths overhead.
The entire rig had been built by the ancients to function as a self-running lung for the lower sector. When the thirty-six-hour tide reached its peak, the rising water-pressure head in the intake well was tuned to exert pressure against an internal balance piston, tripping the gear catch of the balance weight towers. The forty tons of bronze would glide upward along upright guide rails greased with sheep fat and lead paste, opening a sixty-foot throat that could swallow thirty thousand cubic paces of floodwater every minute.
The gate was stalled.
The lower bronze lip of the drop-gate had lifted only four feet above the doorstep runner. Through that narrow slit, thousands of tons of hyper-saline salt water were being forced under tremendous head pressure, producing a screeching, jet-like roar that made the granite walls shudder to their foundations. The balance weight chains overhead were stretched drum-tight, shaking with a high, crystal-clear ping that warned of metal approaching its ultimate sideways tearing force.
Qiao Ming unclasped his wooden ruler from his apron pocket. The fourteen-inch rule, notched with fine brass pins every quarter-inch, was smoothed dark by thirty years of handling. He braced his Jacob’s staff against the wall, leaned out over the void, and measured the water’s rise against the graduation notches carved into the red stone door post.
Four inches in sixty breaths.
The water in the Great Tiered hall behind him had already underwater the eighty tiers of benches. It was creeping up the fluted columns of the western hall, barely three paces below the spring-line of the vaulted ceilings.
He unhooked his sighting disk from his belt to calculate the volume buildup.
The arithmetic was unbending.
If Sluice Nine remained choked at four feet of sky-slit, the inflow from the three converging currents would fully overwhelm the storage capacity of the outer basins within sixty-eight minutes. The water would rise past the high water-marks of the First Epoch. It would spill over the retaining dams of Entry hall 090, flooding into the inner galleries of Entry halls 091 through 100.
In those higher cross-halls lay the dry air domes—the sacred safe halls where ten thousand unawakened statues, the delicate kelp-thick parchment archives of three drowned great realms. The eighteen relic alcoves rested above the reach of common tides.
If eighty feet of hyper-saline mud breached those dry chambers, the chemical solvent of the salt water would dissolve the hardened scriptures within hours. The fragile bones of the ancient ancestors would be swept down the dark channels like dead kelp.
Qiao Ming pocketed his rule and knelt at the lip of the pit.
He unspooled four deep-water lengths of his braided cord, letting the six-sided lead plummet drop into the boiling foam directly before the gate throat. The weight struck something hard two feet beneath the surface—not the smooth, cast face of the bronze drop-gate, but a jagged, unbending mass that jarred the cord with sharp, metal shakes.
He leaned forward, peering through the misty spray with narrowed eyes.
Wedged diagonally across the gate’s southern runner was a giant stone top door beam of white granite. It was twelve feet long and three feet square, weighing at least four tons. It had been torn from the upper gallery of Entry hall 086 by the bore’s first impact and swept down the central nave like a battering ram.
As the gate had tried to lift, the granite block had been sucked into the narrowing intake mouth. One end had jammed securely into the upright bronze track of the drop-gate. Meanwhile, the other end was wedged hard beneath the dropping iron teeth of the backup gear rack.
Behind the stone block, the current had packed a dense, stringy dam of stone-hard driftwood. Waterlogged oak timbers, shattered cedar shafts, and thick mats of iron-hard kelp that had hardened into a composite plug as dense as mason’s mortar.
The forty-ton bronze gate was suspended directly upon the granite top door beam. The full lifting force of the lead balance weights, combined with the high-pressure drag of two million cubic paces of water, was pressing the stone block into the gear teeth like a wedge driven into an anvil.
“A four-ton wedge,” Qiao Ming said softly into his wool collar. “And ninety thousand tons of water holding it fast.”
He stood up. The red stone upkeep ledge beneath his boots was trembling with rhythmic shocks.
Every few seconds, a massive underwater surge would slam into the intake basin. The granite top door beam would groan, grinding tiny clouds of white stone-dust into the boiling green foam, but it wouldn’t budge. The bronze teeth of the gate were biting deeper into the granite with every heartbeat, deforming the metal tracks and threatening to bend the drop-gate so severely that it would never move again.
If the bronze track warped, no human force and no ancient balance weight could ever lift the gate. Water gate Nine would be permanently sealed, and the Great Entry hall would become an underground lake forever.
He walked twenty paces along the narrow ledge toward the southern pier. There, the bronze gear-train was housed within an arched recess of the wall.
The gear housing was giant stone in scale. A main bull-gear ten feet in width was mounted upon a twelve-inch shaft of cold-rolled star-fallen iron, meshed with a series of smaller bronze pinion wheels that drove the balance weight gear catch. The gear teeth, each as broad as a man’s hand, were dripping with black grease that had thickened over the hundreds of years into a waxy, petroleum rind.
Between two of the lower pinion teeth, a splintered fragment of stone-hard cedar was wedged, surrounded by a thick, wet slurry of black silt and crushed shell fragments. The teeth had tried to shear through the wood, but the timber was soaked with quartz dust, hard as chalcedony. The tooth flank was gouged, showing bright, golden bronze beneath the black patina.
Qiao Ming reached out with his bone chisel, scraping away the muck around the axle bearing.
The metal was hot to the touch. The friction of the stalled motor, fighting against the relentless upward pull of the balance weight towers overhead, had heated the glowing-bronze bearing until the animal fat grease was smoking. A faint, acrid smell of scorched oil and sulfur rose from the housing, stinging his nostrils and mingling with the cold, wet air of the pit.
He examined the main drive axle with his fingers. The surface of the cold-rolled iron was scored with fine spiral fissures—twisting stress marks created by the balance weight chains pulling against the locked teeth. If those fissures propagated across the width of the shaft, the axle would snap with the sound of a thunderbolt. The forty-ton drop-gate would drop into the doorstep like a guillotine, severing the bronze runners and crushing whatever lay in the throat.
He looked up at the ceiling pulley wheels.
High in the gloom, eighty arm-lengths above the roaring water, the great bronze pulleys were weeping thick streaks of black stone oil that fell into the flood like dark tears. The iron cables were humming at a hum that made his teeth ache through his jaw.
He couldn’t cut the chains. That would drop forty tons of bronze onto the doorstep and seal the gate entirely. He couldn’t pry the top door beam from this high ledge. The distance was too great and the angle of leverage was impossible from above.
There was only one place where Archimedean force could be applied to the stone’s shear plane.
He would have to go down into the throat.
He would have to enter the underwater gear chamber beneath the drop-gate, find the hairline fracture running through the granite top door beam, and split the stone from within the current itself.
Above him, the air in the high barrel vault gave a sharp, wet thud.
It wasn’t the sound of falling stonework. It was the sound of tightly packed air—the first warning that the air trapped against the ceiling was beginning to turn into an air-powered piston. The sound carried a bone-shaking shock that rippled through the water, sending small, stinging shakes into the soles of his feet.
The water was rising past the seventy-sixth tier of the tiered arena benches. Down in the basin, the green foam was climbing toward the red stone ledge, wetting the soles of his boots and sending cold tendrils of salt water swirling around his ankles.
The time for surveying was over. The flood was closing the sky, and the stone was waiting for a hand.