Framing forty independent wooden arch centerings was the supply equivalent of building an entire second town just to burn it down.
At dawn, Giles Croft stood on the upper narrow high walkway of Pier Eighteen, sixty feet above the rocky gorge. Below him, Master Caleb Thorne-Wood was assembling a massive wooden rig that looked less like building scaffold and more like a siege tower on rollers.
“Traveling centering overhead frame,” Giles said, inspecting the joinery. “Standard clip-on formwork. Instead of framing timber for every bay, we build four mobile timber frames. We pour an arch, allow forty-eight hours for first set, strike the folding wedges, and roll the entire assembly along wooden rails to the next pier.”
Caleb tapped an iron-rimmed ash wheel with his heavy boot.
“Four frames for forty arches,” Caleb said. He ran his calloused hand over the seasoned oak hub. “It cuts our lumber consumption by ninety percent and saves two months of saw-pit sweat. But my lord... Will forty-eight hours be enough for the green stone to hold its own weight?”
“Volcanic cement high-pressure concrete achieves sixty percent of its ultimate crushing strength within forty-eight hours,” Giles explained. He opened his wooden ruler. “A half-round arch with an eight-foot rise and a twenty-foot span generates pure crushing thrust. Once the keystone section is tamped, the arch locks under dead load. It doesn’t need the wood.”
The physical variation in pier heights presented an immediate building obstacle.
Across the two-mile transect, the terrain dipped and rose wildly. The shortest piers on the valley terraces stood barely twelve feet high. Meanwhile, the four deep river piers in the canyon deep pit rose sixty feet above the churning rapids.
To maintain a level rail bed for the traveling gantries, Giles designed clip-on timber stacked timber frame.
Heavy spruce ties were stacked in alternating crisscross courses atop the pier caps, supporting nonstop lengthwise stringers of seasoned white ash. The stringers were spiked to the stacked timber frame with six-inch wrought-iron dogs and greased with thick sheep fat.
On Bay Sixteen, the forward left wheel of Gantry Two hit a rough grain knot in the ash stringer, wedging tight with a metal screech.
“Hold the team!” Caleb bellowed, waving his arms at the ox driver.
The two draft oxen strained against their leather yokes, their hooves slipping on the greased timber.
Master Borin Bronze-Lung climbed up the ladder with an iron screw-jack balanced on his shoulder. The dwarf had forged three of the clockwork jacks for quarry work. It used square-threaded iron screws turned by a heavy crossbar.
“Stand aside, wood-carver,” Borin grunted, wedging the jack’s foot under the overhead frame carriage. “Let real metal lift the load.”
Borin hauled on the crossbar. The iron screw turned with a dry squeak, lifting the five-ton wooden carriage two inches into the air.
Caleb leaned over the rail with a curved drawknife, shaving the stubborn spruce knot flush with three swift strokes.
“Drop her down, Borin!” Caleb called.
Borin reversed the jack. The iron-rimmed wheel settled cleanly onto the shaved rail. The oxen leaned into their collars, and the massive overhead frame rolled forward into the next bay with a smooth, rhythmic clatter.
The construction became a timed together heavy-duty ballet.
Four mobile timber gantries rolled along the ash stringers across forty pier stations. Each overhead frame carried a curved half-round deck of seasoned ash, supported by pairs of greased oak folding wedges.
The concrete crews worked like clockwork across four timed together teams.
Crew Alpha tamped the stiff volcanic cement concrete into the forms of Bay Twenty. They shoveled the dense, dark-gray paste into wooden skips, hoisting them on derrick pulleys to the upper narrow high walkways using ox-powered gin poles.
Duncan’s quarry apprentices drove heavy oak rammers into the wet mass, expelling trapped air until moisture rose to the surface with a glossy sheen.
Sister Teresa climbed the work frames twice a day, carrying buckets of clear wet lime plaster water to spray over the curing concrete.
“Bless the stone, Sister,” Duncan called down from the narrow high walkway, grinning through his white dust.
“I’m sealing the pores of the faithful,” Teresa replied, pumping her brass syringe. “The lime water keeps the skin moist so the devil of cracking finds no purchase.”
“She’s preventing plastic shrinkage cracking by maintaining surface moisture in the air above ninety percent,” Giles noted to Toby. “Her chemical gearwork is entirely sound, even if her nomenclature is ecclesiastical.”
Crew Beta struck the wedges on Bay Nineteen.
With heavy iron sledges, two carpenters struck the greased folding wedges at the same time. The wedges jumped back three inches. The massive wooden ribs of the falsework groaned. He settled downward away from the underside of the newly cured concrete arch.
The arch settled less than an eighth of an inch, locking immovably against the pier springlines.
Crew Gamma hitched two draft oxen to the overhead frame carriage.
With a spray of sheep fat and a groan of iron axles, the twenty-ton wooden rig rolled forward along the greased ash rails, advancing twenty-four feet to Bay Twenty-One in less than fifteen minutes.
Crew Delta dressed the outside faces with thin granite cut stone veneer.
Master Duncan and six masons laid dressed gray granite blocks along the outer spandrels, bonding the stone skin with high-pressure volcanic cement mortar. The stone facing protected the green concrete core from wind erosion, moisture penetration, and winter frost flaking off.
Toby Karr ran along the high narrow high walkways with a plumb-bob and a bucket of red chalk, checking the crown height of every arch.
“Bay Twenty-Four true to the eighth of an inch, Lord Giles!” Toby called, his voice bright against the mountain wind.
The apprentice land-mapper was in his element, copying Giles’s careful gait. He moved from station to station with his measuring rod.
Down below, settlers from the centuriation grid gathered along the valley trails. It stared up into the sky.
Arch after arch spanned the void. Across the two miles between Eagle Peak and Grey Crag, the forty concrete arches formed an unbroken, majestic stone ribbon that leaped across chasms, bounded over granite spurs, and marched high above the roaring river gorge.
To the pioneers, who had lived their lives in low timber hovels, the soaring stone viaduct was breathtaking.
“A rainbow of living rock,” an old weaver whispered. His eyes were wide as he watched the oxen roll the wooden chariot across the sky. “The Lord Master builder walks above the clouds, laying down highways for the angels.”
“It’s not a highway for angels,” Giles muttered as he climbed down the ladder. “It’s an unreinforced concrete viaduct carrying a three-and-a-half-foot box-shaped water chute with a two-inch high-pressure plaster lining.”
Inside the upper channel, Duncan’s plasterers were applying the final coat of waterproof mortar.
The plaster was made from three parts finely ground fiery volcanic cement, two parts wet lime plaster, and clean quartz sand, troweled with flat iron floats until the surface was smooth as glass.
“No leaks,” Duncan said, running his rough palm along the cured plaster. “Smooth as a maiden’s cheek. Water will slide through this like grease on a hot skillet.”
Lady Millicent walked along the lower raised stone road, reviewing the project accounts with a critical eye.
“Three hundred and twenty barrels of high-pressure lime,” Millicent tallied aloud. “Six hundred tons of crushed dark rock aggregate. Fourteen barrels of sheep fat for the axles. The total cost of the arches sits at eight hundred gold sovereigns in material and wages.”
“And the asset value?” Giles asked, adjusting his glasses.
“Priceless,” Millicent replied with a rare, approving nod. “A permanent town water artery that increases the real property valuation of every insula in Grey Crag by two hundred percent.”
By the sixth afternoon, the final arch—Bay Forty—was keyed into the stone gatehouse stronghold of Grey Crag.
The two-mile raised water highway was complete.
Giles walked the entire two-mile length of the upper narrow high walkway with Kenneth Drake and Toby. From Eagle Peak to the settlement, the covered channel sloped down at a steady, barely noticeable slope of one in five hundred.
The top of the channel was decked with heavy stone flags. That created a raised walkway six feet wide that doubled as an unbeatable defensive narrow high walkway.
Kenneth ran his hand along the stone low roof wall. He looked down at the valley road forty feet below.
“Look at this line-of-sight,” Kenneth said, his tactical eye gleaming with skilled appreciation. “An raised raised stone road spanning the entire valley. A squad of crossbowmen up here could dominate the southern approach for a mile in every direction. An enemy can’t climb it, can’t burn it, and can’t undermine it.”
“Its main function is high-pressure delivery, Kenneth,” Giles said. “Defensive work is merely a backup load-bearing byproduct.”
“In a siege, my lord, backup byproducts are the ones that keep men alive,” Kenneth countered with a rare smile.
Kenneth leaned over the stone rail, pointing toward the southern defile.
“If Warlord Bronn brings his five hundred axemen down that road, we can station twenty archers on Arch Thirty-Eight. They can shoot straight down into his vanguard without taking a single counter-arrow. The low roof wall provides full breastplate cover.”
“And the stone absorbs moving impacts,” Giles added. “Even if they deploy twisting force giant crossbows, unreinforced concrete arches fade shaking energy into the granite abutments.”
The sun was sinking behind the western ridges, casting long, purple shadows across the valley.
Giles climbed the final timber ladder to the high pool intake at Eagle Peak.
Behind a heavy oak water gate, the Roaring Maiden spring formed a deep, crystal pool of pure snowmelt, held back by a volcanic cement concrete weir.
Teresa stood beside the gate, holding a small brass amphora of olive oil. Master Duncan, Caleb, and Millicent stood along the intake wall, silent with excitement.
Giles took his brass pocket watch from his vest, checking the second hand.
“Pool head is at twelve feet,” Giles announced. “Channel is swept and inspected. Flow rate calculated at five hundred gallons per minute.”
Borin Bronze-Lung stepped up beside the weir, his sight fire gauge tucked safely in his coat. He held a brass grease cup, checking the threaded spindle.
“The screw is greased with animal fat and lard, Lord Giles,” Borin muttered. “Turn her smooth. If the bronze collar chatters under head pressure, back her off half a turn and let the water seat the gate.”
“A controlled high-pressure release,” Giles agreed, his fingers tightening on the iron rim. “We don’t introduce dynamic water hammer into an empty channel.”
He reached out and took hold of the iron hand-wheel on the water gate.
“Time to open the tap.”