The wooden charging platform on the fire crown hung suspended thirty-five feet above the bustling foundry yard.
From this raised timber deck, Giles Croft could see the entire heavy-duty terrace laid out with sharp-angled clarity.
To the north lay the newly opened Under-Pass, where dwarven ox-drays were unloading white sacks of kaolin and baskets of coal.
To the south, the great copper drain tube arched over the granite dyke like a shining wire. It poured fourteen hundred gallons of clear water every minute into the drainage cut.
And directly below, stacked in neat, color-coded bays along the inclined timber railway, lay the raw materials that would wake up the stack. Red bog-iron ore, black peat coke, and white crushed limestone.
Giles stood beside the charging throat. His folding wooden ruler was held against the iron lip of the bell-hopper.
“A blast fire isn’t an incinerator,” Giles lectured. He turned to Toby Karr and three apprentice loaders. “It’s a counter-current chemical reactor.
Gas flows up. Solids go down. If you dump materials at random, the gas channels through the path of least pushback, leaving cold dead zones in the core. The burden must be charged in strict alternating strata.”
Toby Karr crouched by the hoist cable, his tally-slate balanced on his knees.
“First layer is the kindling bed, Lord Giles,” Toby recited, checking off items with his pencil.
“Twelve cords of seasoned pine splits, followed by four tons of lump peat coke to establish the first burning hearth.”
“Correct,” Giles said. “Then begins the production burden.
One skip of roasted limonite, followed right away by two skips of peat coke, capped with half a skip of crushed limestone. That maintains an ore-to-coke ratio of two-to-one by weight, with fifteen percent basic flux.”
“And the chalk?” Master Duncan Stone-Splitter asked, leaning over the handrail with his sledge resting on his boots. “Why feed good mountain limestone into a fire that wants to eat iron?”
“Stoichiometry,” Giles replied, pulling his slide rule from his vest pocket. “Bog-iron ore is heavily contaminated with quartz dust—plain quartz sand.
At smelting heat levels, quartz dust doesn’t burn. It melts into a thick, sticky, acidic glass with a melting point over seventeen hundred Celsius. If we don’t flux it, that thick, sticky glass will coat the dropping coke lumps, choke the draft, and freeze the hearth into a five-ton solid lump of dead stone.”
Duncan scratched his thick beard. “So the limestone eats the sand?”
“The white lime-chalk calcines into calcium oxide,” Giles explained, moving the runner on his slide rule. “The basic calcium oxide reacts with the acidic silicon dioxide to form liquid calcium stone-glass—melted rock waste.
It has a much lower melting point, around twelve hundred Celsius. It liquefies fully, floats on top of the heavier molten iron like oil on water, and washes the sulfur out of the metal bath.”
Lady Millicent Croft climbed up the wooden access stairs, her double-entry thick parchment ledger open against her forearm. She gave Lady Beatrice a polite, measuring nod. Then she turned her attention directly to the inventory totals.
“Duchess Rowena currently expends twenty-two thousand gold sovereigns annually importing bar-iron through the southern river tariffs,” Millicent said, her tone as precise as a surgeon’s blade.
“Every hundredweight of southern iron carries an eight percent toll at Rivermouth, a six percent transit fee through Baron Cedric’s locks. An unrecorded surcharge for carriage breakage along the muddy turnpikes.”
Lady Beatrice raised an eyebrow, adjusting her glasses. “You seem remarkably well informed regarding the private expenditures of the Highmarch exchequer, Lady Millicent.”
“I keep books, Lady Beatrice,” Millicent replied without looking up from her figures.
“When one keeps books for twenty years, the incompetence of neighboring baronies becomes a matter of basic arithmetic rather than state espionage. If Grey Crag produces ten tons of pig iron per heat, we can deliver refined merchant bar to Highmarch at forty percent below the southern merchant guild’s cartel price, even after accounting for mountain haulage.”
Beatrice’s eyes narrowed with keen mercantile interest. “Forty percent below cartel rates? The Guild of Ironmongers in Dunwall would riot in the streets.”
“Let them riot,” Millicent said calmly. “Riots eat cloth and produce scrap iron, both of which we’ll happily purchase at a discount.”
“Alchemy,” an elegant, cool voice drifted up the wooden ladder-well. “Pure, pure high alchemy, spoken with the dry tongue of an estate clerk.”
Giles turned as Lady Beatrice of Dunwall stepped off the top rung of the access stair. She was followed by two ducal guards in burnished mail.
She wore a dark green riding habit trimmed in silver fox fur. Her auburn hair neatly was bound beneath a velvet toque.
A pair of delicate gold-rimmed glasses sat upon her straight nose. Her keen, dark eyes took in the timber hoist, the brick stack, and the roaring waterwheel with cool high-born care.
“Welcome to the charging gallery, Lady Beatrice,” Giles said, not bothering to put away his rule. “Mind the dust on your cuffs. Peat coke soot has high adhesion.”
Beatrice walked to the edge of the iron bell-hopper. It peeked down into the dark, forty-foot brick shaft.
“Duchess Rowena sent me south to verify a wild tale,” Beatrice said, her voice smooth as polished silk.
“The river boatmen reported that Baron Croft had built a tower of Babel upon the Black Fen, a stone chimney that breathes like a dragon and vomits thunder. I expected to find an army of sorcerers chanting over sulfur pots.”
She turned, looking Giles up and down with sharp amusement.
“Instead, I find an exiled court engineer in a soot-stained waistcoat, weighing red dirt and chalk in grocery scoops.”
“Grocery scoops are much more dependable than sorcerers,” Giles said mildly. “Sorcerers demand blood sacrifices and suffer unpredictable spell failure rates. A balance scale never fails to report gravity.”
Beatrice tilted her head, her glasses catching the autumn glare. “And with this red dirt, Lord Croft, you expect to supply weapons fit for the northern legions?”
“I expect ten tons of high-grade pig iron every twenty-four hours, Lady Beatrice,” Giles replied.
“Which Borin can convert into five tons of rolled plate, forty thousand nails, or three hundred steel broadheads by sunset tomorrow. Mind your step. Your silk slippers are within twelve inches of the hoist cable.”
Beatrice smiled thinly, stepping back to a safer vantage point beside Toby’s tally desk. “Duchess Rowena will be fascinated to learn that the balance of northern power now rests upon calcium metasilicate.”
“The balance of northern power has always rested on metalworking,” Giles said. “Rulers simply preferred to pretend it was divine right because prayers are cheaper than blast furnaces.”
THWUMP.
The first heavy wooden skip climbed the inclined timber frame stand, pulled by a steel wire rope wound around the waterwheel’s backup drum.
The skip tipped forward. With a hollow, echoing roar, three tons of dry peat coke tumbled through the hopper throat. It plunged down the brick shaft to settle upon the kindling bed below.
“Charge layer one complete,” Toby called out, chalking the tally-slate. “Coke bed depth is six feet!”
“Hoist skip two,” Giles commanded. “Roasted limonite nodules. Spread the charge evenly across the bell outer edge.”
The second skip climbed the rails, dumping two tons of dark crimson iron gravel into the throat. A red cloud of dust puffed upward, smelling of roasted rust and hot stone.
Next came the limestone flux. Two thousand pounds of dazzling white spar-stone sand that coated the red ore like a dusting of fresh snow.
Layer by layer, the forty-foot shaft was filled.
Thirty tons of roasted ore, fifteen tons of pressed peat coke, and four and a half tons of limestone flux disappeared into the maw of the stack, until the burden column reached within six feet of the charging doorstep.
Down at the base of the fire, Master Borin Bronze-Lung was waiting by the main air tuyeres with a five-foot pitch torch.
“The stack is burdened, Lord Giles!” Borin bellowed up the access hatch. “Draft gates are cracked! Shall I light the hearth?”
Giles checked his pocket watch. It was exactly four o’clock.
“Ignite the kindling, Borin,” Giles called down. “Start with natural draft for thirty minutes until the coke bed catches, then engage the piston blowers at quarter-throttle.”
Borin plunged the flaming torch through the central lighting port.
Inside the dark crucible, dry birch splits and pine tar caught instantly. A hungry, crackling orange glow bloomed behind the copper tuyere check glasses.
Within ten minutes, the kindling heat reached the lower peat coke layer. The coke ignited with a low, underground rumble that shook through the foundation slab.
At first, a thin ribbon of blue flame danced across the surface of the burden at the top throat.
Then, without warning, the wind shifted.
A sudden, violent downdraft swept off the northern bluffs, slamming down into the open fire throat.
WHOOOOSH.
A choking cloud of dense, greasy black soot erupted from the hopper, engulfing the charging platform in an eye-stinging fog.
Toby coughed wildly, dropping his chalk-slate. Lady Beatrice staggered backward. She grabbed her silk handkerchief to her face as her guards drew their swords in blind panic.
Down below, the steady rumble of burning began to sputter and die.
Down along the river quay, Judge Malric Ostrander watched the plume of black soot billow from the fire stack.
The gaunt judge stood upon the forward deck of his black-hulled galley, his black glass woolen mantle whipping in the north wind.
His clerk sat beside him on a camp stool, dipping an iron-tipped pen into dark ink.
“Record it, Brother Matthew,” Ostrander murmured, his eyes glittering with cold ecclesiastical satisfaction. “The black throat chokes.
The earth rejects the unnatural burden of the pit. Write that the unblessed tower vomits the dark bile of failure.”
“Shall we summon the paladins to seize the platform, Father?” the clerk whispered.
“Not yet,” Ostrander said, raising his hand. “Let the failure complete itself.
When the iron freezes inside the stone, the Baron will be ruined. His laborers will turn on him for wasted bread, and the Synod will dismantle this pagan chimney brick by brick without striking a single blow.”
Borin’s voice came shouting up the voice-pipe, shrill with alarm.
“Lord Giles! Core heat is dropping! The thermocouple reads only seventeen hundred degrees! The draft has reversed! The fire is choking on its own throat!”
Giles stood at the railing, coughing once into his wool sleeve, his eyes fixed on the sluggish black smoke swirling in the throat.
“The incoming cold blast is cooling the hearth enthalpy,” Giles muttered, pulling his rule. “The air is entering the tuyeres at sixty degrees Fahrenheit.
It’s absorbing more heat energy than the burning can generate. Cold blast has hit its heat-powered limit.”
He turned toward the ladder, his face hard and decisive.
“Toby, don’t drop the slate. Borin, hold the blowers steady. We need a hot-blast regenerator, and we need it before the burden freezes.”