The lower trench of the iron quarry was a deep pit that sunlight had forgotten ten thousand years ago.
Three hundred feet below the mountain rim, the heat hovered just above freezing. Water seeped from the dark slate strata in steady, rhythmic drops, pattering into the drainage gutters with the relentless rhythm of a water clock. The only light came from iron fire bowls burning rotten-egg bituminous coal. It filled the stale air with an oily, yellow smog that coated the throat in soot.
Lin Tao knelt by a mound of fresh shale tailings, his left arm held tightly against his ribs.
His broken collar bone throbbed with an angry, inflammatory heat. With every breath, the sharp edges of the fractured bone rubbed against the surrounding muscle tissue. It sent hot waves of nausea up into the base of his skull. He couldn’t swing a sixteen-pound sledge. If he tried to lift an iron pick, the shearing force would rip the subclavian artery. He would bleed to death inside his burlap tunic within two minutes.
Work through leverage, he thought coldly, forcing his breathing into slow, four-second cycles. When hardware is damaged, optimize the execution path.
At the mouth of the drift sat Old Man Geng, squatted on a three-legged stool before a small charcoal forge.
Geng was seventy years old, his spine curved like a sickle from fifty years of breathing rock dust. His milky, clouded eye-clouded eyes were fixed on the dull orange coals as he worked a set of goatskin bellows, heating a row of worn iron chisel heads to temper them in a trough of stale salt water.
Lin Tao walked toward the forge, keeping his footsteps deliberate and quiet.
“Elder Geng,” Lin Tao said, stopping two paces outside the heat of the fire bowl.
The old smith didn’t look up from his coals. His breath rattled in his withered chest like dried peas in an earthen jar. “The punishment overseers took your bread ration this morning, boy. I have no millet cakes to share with a dying mouth.”
“I didn’t come for grain,” Lin Tao said.
He reached into his hemp belt with his right hand. He pulled out a small, irregular nugget of native copper, roughly the size of a pigeon’s egg, heavy and cold as ice. The metal was not smelted. It had the rough, crystal-clear surface of raw ore pulled from an underground vein.
He had pulled out it from the unrendered shape seam behind the collapsed slate slab in drift four.
Lin Tao placed the copper nugget on the greasy wooden rim of Geng’s water trough.
Old Geng paused his bellows. His milky eyes widened, his head tilting toward the metal clink. He reached out with a scarred, callused thumb. He rubbed the metal’s rough surface. He tested its thickness with the instinct of a man who had worked metals since the last dynasty.
Native copper was exceptionally rare in the upper shale beds. The potion-made students at Cloud-Mist Peak paid two silver bits an ounce for pure virgin copper to cast fire cooling sleeves.
“Where did you steal this, boy?” Geng whispered, his voice trembling with sudden terror. He looked past Lin Tao’s shoulder toward the dark haulage tunnel. “If Overseer Hu sees this in your palm, he will peel the hide from your ribs and hang you from the overhead frame.”
“The stone gave it up when the ceiling broke,” Lin Tao said smoothly. “The overseers know nothing of it. I want six inches of your cold-drawn crucible wire. The thick gauge used to bind the fire crucibles.”
Old Geng stared at Lin Tao for five long heartbeats. His scarred fingers curled tightly around the copper nugget. He pulled it into the greasy folds of his apron like a rat dragging grain into a hole.
Without speaking, Geng reached beneath his anvil log. He dragged out a coil of stiff, cold-drawn iron wire. Wire forged from high-carbon ore and cooled in salt water to withstand the huge heat swelling of molten bronze.
The old man took a pair of heavy iron shears, gripped the wire at the six-inch mark. Then he squeezed with both hands.
Snip.
The six-inch length of dark iron fell into the stone dust between Lin Tao’s boots.
“Take it and get out,” Geng rasped, resuming his slow pumping of the bellows. “If you die in the trench today, I never saw your face.”
Lin Tao picked up the wire. He carried it thirty paces away to an abandoned sandstone grindstone sitting in the shadow of a drainage timber.
He sat on a dry boulder, took the cold iron wire in his right hand. Then he began to grind.
He didn’t fashion a knife or a dagger. In a penal labor quarry, carrying an edged weapon was a death sentence. The first guard who saw a blade would execute him for insurrection.
Instead, Lin Tao ground the tip into a slender, four-sided plumb-point, perfectly centered along the lengthwise axis of the wire. He used a sharp shard of quartz crystal to score three precise, tiny rings around the blunt tail. That created a tactile grip that wouldn’t slip in sweaty fingers.
Four inches long. Cold-drawn iron. Perfectly balanced.
A tuned test land-mapper’s metal pen.
Lin Tao held the iron needle between his right thumb and forefinger. He closed his right eye, focusing his concentration entirely through his left.
The dark quarry walls transformed.
The black slate lost its opacity, resolving into a fine, detailed web of glowing load-bearing vectors. Thousands of tiny white stress lines ran through the bedrock, crisscrossing the cave ceiling like spider silk.
Lin Tao tracked the stress lines as they came together.
They didn’t fade into the mountain. They flowed directly toward a single dark point forty feet above the central haulage track. A load-bearing fault where the sedimentary shale layer had separated from the underlying solid mountain stone.
“The entire ceiling is hanging by three inches of lime mortar,” Lin Tao muttered.
Thirty paces ahead, Tie Shan was heaving two-hundred-pound boulders into his cart with rhythmic, robotic endurance. The giant’s broad back glistened with frost and cold sweat, clueless to the mountain above him.
Directly over Tie Shan’s head, the convergence point of the stress vectors was glowing a bright, toxic amber.
A sound like dry kindling snapping echoed across the high ceiling arches.