The southern gully was an office outrage. It was twenty-four feet across, twelve feet deep, and full of cold mountain mud.
Two days after the under-road drain cleaner broke Sir Gareth the Cleaver’s iron pavilion shield, the southern approach remained blocked. Every cart of stone from Master Duncan’s granite ridge had to crawl two miles through pine scrub. A single round trip took four hours. Oxen threw shoes in the peat. The settlement’s stonework schedule was losing twenty-five man-hours every shift.
Giles Croft stood on the rim of the gully with his brass rule open.
Down in the mud below, Sir Gareth was shoveling river gravel into a barrow. His left arm was bound in split cedar splints.
“Keep your back straight, pawn,” Giles called down. “Lift with the knees. An ergonomic stance reduces lower-back strain. If you blow out a vertebra, your aggregate haul drops to zero.”
The disgraced knight stopped his shovel. He looked up, mud dripping from his beard.
“I was a knight banneret of the Third Circle,” Gareth croaked. “Now you have me hauling ditch pebbles like a bondman.”
“You were running a secret military assembly on a loose road,” Giles replied. “The court assessed thirty tons of aggregate for stone floor rutting. You have moved four tons. Cease whining and resume shoveling.”
Captain Kenneth Drake paced the lip of the ravine, his ten-foot iron-shod pacing rod across his chest.
“He shovels slow, my lord,” Kenneth said. “Give me half an hour with a switch and I’ll double his tonnage.”
“No corporal punishment,” Giles said. “Pain causes a negative mood debuff and increases accident hum. Let him shovel at standard pace. Our problem is this ravine.”
Kenneth peered into the deep gap. “We could lay two pine stringers across the top and deck them with birch.”
“It would rot in eighteen months,” Giles said. “And the first six-ton block of dressed granite from Duncan’s quarry would snap the stringers. We need a permanent arch.”
Master Duncan Stone-Splitter came along the bank, his apron dusted white with limestone flour. He carried a heavy iron splitting hammer.
“You want to span twenty-four feet without a single prop beneath it?” Duncan asked. “Lord Giles, stone doesn’t float. If you pour gray mud across empty air, it will snap the moment the wet leaves it.”
“Stone has zero pulling capacity,” Giles said. “It won’t tolerate bending. But it has tremendous crushing strength. In a segmental arch, gravity doesn’t pull the material apart. Gravity squeezes it together.”
Giles took a smooth pine shingle from Toby Karr. With a pencil, Giles sketched the profile.
“The curve follows the inverted catenary line of thrust,” Giles explained. “Every pound of dead weight and live weight travels downward and outward along the curve into the solid mountain stone on either bank. The stone is never pulled. It’s only pressed.”
Duncan scratched his beard. “And what holds it up while the mud turns to rock?”
“Falsework,” Giles said. “Caleb, bring up the ribs.”
* * *
Master Caleb Thorne-Wood had spent two days in the saw-pit shaping white spruce.
He and four joiners brought two half-round wooden frames up the trail on a low cart. Each frame was twenty-four feet long, built from thick spruce planks braced by streaming struts.
“Centering ribs,” Caleb grunted. “Cut to a seven-foot rise. If this timberwork sags under your wet mud, my lord, I’m jumping into the ditch after it.”
“It won’t sag if the wedges are true,” Giles said.
Under Giles’s direction, the joiners erected the two ribs across the gully. Giles had Caleb set the posts upon pairs of greased hardwood folding wedges.
“Why the wedges?” Kenneth asked, tapping one with his rod.
“Once thirty tons of concrete cures on top, you can’t pull the frames out,” Giles told him. “When the cure is finished, we strike the wedges with a mallet. The wedges slide back, the timber drops two inches, and the centering rolls free.”
Kenneth looked at the greased oak wedges, then gave a short nod. “A strike of a mallet drops the scaffold. Simple.”
“Standard formwork building,” Giles murmured.
Once the ribs were braced, Caleb’s crew nailed narrow three-inch spruce battens across the curved upper face. It created a smooth wooden trough spanning the void.
Then came the concrete.
Duncan had two crews working the mixing pans. Four barrels of reddish fiery volcanic cement ash from the Old Fire Pit were blended with two barrels of freshly slaked burning lime powder from the upright shaft kiln. They shoveled in dark rock grit, washed river gravel, and five buckets of river water, working the mixture with iron hoes into a stiff, dark-gray paste.
“Tamp it in six-inch lifts,” Giles ordered, climbing onto the narrow high walkway. “Start from both springlines at the same time. Advance toward the crown at equal speed. If one side gets heavy, the centering will twist.”
For two days, eighteen men worked in rotation. Sir Gareth dumped gravel into the mortar troughs until his tunic was soaked. Laborers hoisted wooden buckets on pulleys, pouring the slurry onto the curved wooden barrel. Duncan and his apprentices tamped the paste with heavy oak rammers, driving out air pockets.
By the second evening, the gray mass met at the crown. Giles had them smooth the roadway surface with flat river slates, sloping the crown two inches toward the edges for runoff.
“Now we wait,” Giles announced, wiping his brass measuring tongs.
“How long?” Kenneth asked. “My scouts smell smoke on the south wind.”
“One hundred and twenty hours,” Giles said. “Five days for the high-pressure bond to form. Keep the surface covered with wet straw. If the top dries too fast, surface shrinkage causes map cracking.”
Duncan stared at the straw-covered mound. “Five days? And then it will hold a wagon?”
“It will hold six wagons,” Giles said.
* * *
On the fifth morning, frost coated the hemlocks. But the gray arch was cool and solid beneath its blanket.
Settlers gathered at the rim of the gully. Sister Teresa stood with her brass slurry lance resting against her shoulder, watching the straw. Settlers whispered among themselves, wondering if the gray heap would tumble into the mud the instant the timber came out.
Giles climbed down to the western bridge pillar with a sledgehammer.
“Caleb,” Giles called. “Clear all personnel from beneath the span. If the arch shears, run toward the rock bank.”
Caleb stepped thirty paces down the gully. Duncan gripped his dressing scutch with white knuckles.
Giles stepped up to the main folding wedge on the north post. He swung the sledge.
CLANG!
The iron head struck the greased hardwood wedge. The wedge slid three-eighths of an inch. A sharp crack echoed off the ravine walls as the framework shifted.
“Stand your ground,” Giles ordered calmly. He walked to the friend wedge and struck it with equal force.
CLANG!
The second wedge jumped back. Giles moved to the south bridge pillar and struck the southern wedges in set. With a low groan of stressed timber, the spruce centering ribs dropped two inches.
The wooden forms fell away from the underside of the gray concrete.
The crowd went fully still.
The twenty-four-foot arch of stone hung suspended in the empty air. It didn’t drop. It didn’t crack. A puff of lime dust drifted from the springline as the concrete settled three-sixteenths of an inch. It locked itself against the solid mountain stone.
Duncan Stone-Splitter let out his breath. He scrambled down the bank and reached up to touch the smooth, curved underbelly of the arch.
“It holds,” the dwarf whispered, his fingers stroking the cold curve. “No joints. No keystone. A single tooth of stone, sprung from cliff to cliff without a prop.”
“It’s water-setting concrete, Duncan,” Giles said. “It will gain strength over the next three hundred years.”
Sister Teresa raised her chin, her eyes shining with zeal. “He commanded the dust of the volcano and the water of the river to become an unbroken path. Clean. Seamless. A bridge that knows no decay.”
“It knows freeze-thaw cycles,” Giles muttered, checking his pocket watch. “Which is why we installed lateral deck drains. Kenneth, bring up the test load.”
Kenneth whistled shrilly between his teeth.
From the quarry road came the clatter of iron-rimmed wheels and the lowing of oxen. Two massive freight wagons, each loaded with four tons of dressed cut stone blocks, rumbled down the trail behind four heavy draft oxen.
The wagon drivers halted at the edge of the new concrete deck, their faces pale.
“Drive them onto the crown,” Giles commanded.
“My lord!” the lead driver stammered. “The stone is green!”
“Drive them to the center and set the brake,” Giles repeated.
The driver swallowed and cracked his whip. The four oxen leaned into the yokes. The heavy iron wheels rolled onto the smooth volcanic cement concrete. The sound changed instantly from the wet squelch of peat to a sharp, ringing clatter.
The two wagons rolled to the center of the span. Eight tons of granite, two tons of timber wagons, and four oxen stood motionless directly over the deep gap.
Giles stood at the bridge pillar with a brass feeler gauge, checking the gap at the springline. Then he sighted across the crown with his pocket spirit level.
The bending was eight thousandths of an inch.
“Load-bearing settlement is well within elastic settings,” Giles announced. “Live load capacity confirmed at twenty-two tons. Master Duncan, resume heavy stone hauling right away.”
A cheer went up from the quarrymen. Toby snapped his chalk-reel against a timber stake, grinning broadly.
The cheer was cut short by the wild beat of hooves.
A bay mare burst from the southern woods, lather dripping from its chest. Slumped over its neck was an older man in a torn wool merchant’s mantle. A black-fletched crossbow bolt was buried three inches deep in his left shoulder blade, the wool around it soaked in bright crimson.
Kenneth moved quickly. His ten-foot iron-shod rod caught the horse’s halter, jerking the exhausted beast to a halt.
The rider rolled out of the saddle, hitting the concrete deck with a wet thud.
“Master Corbin,” Kenneth said, checking the fallen man’s pulse. “The grain factor from Oakhaven.”
Giles stepped forward, his eyes narrowing as he noted the broadhead lodged beneath the man’s collarbone.
“Breathe shallow, merchant,” Giles said, pressing a clean linen cloth firmly against the wound. “Teresa, fetch the razor-sharp kit and boiling water. Kenneth, secure the horse.”
The wounded merchant gripped Giles’s sleeve with shaking fingers. Blood bubbled at the corner of his lips.
“The Broken Horn...” Corbin wheezed. “They have closed the pass. Five hundred men under Warlord Bronn. Burning every steading. Killing every wagon driver.”
“We repelled their raiding party two days ago,” Kenneth said. He gestured toward Sir Gareth in the ditch. “We took Sir Gareth.”
“Not a raid,” Corbin gasped, coughing blood onto the gray concrete. “An army. Bronn found out you took Gareth. He took an oath on his flaming brand. He’s marching on Grey Crag with rams and towers. He swore he will roast your Lord Master builder in his own lime kiln!”
The merchant’s head fell back against the stone, his eyes rolling back as blackout took him.
Teresa was already there, applying pressure and packing clean moss into the wound.
Silence dropped upon the bridge. The cold wind howled through the hemlocks, carrying the faint smell of distant woodsmoke.
Kenneth slowly stood upright. He looked down at the blood spreading across the new arch. Then he turned his gaze south toward the dark forest.
“Five hundred men,” Kenneth said softly. “Two siege towers. And we have fifty spears.”
Giles wiped Corbin’s blood from his fingers with a rag. A grim weight settled behind his ribs. He looked at the unconscious merchant, then at the blood on the clean gray stone. Men were dying out there in the scrub. Real blood, real bone, and an army marching to burn them out.
Then he looked down at the bridge beneath his boots—twenty-four feet of solid, rock-steady stone.
“Five hundred men will need fifteen hundred pounds of grain every twenty-four hours,” Giles said in his standard dry tone. “Their supply line is stretched across forty miles of hostile peat. If they bring siege towers across loose roads, their rolling pushback will exceed eight hundred pounds of drawbar pull per axle.”
He turned back toward the settlement.
“Toby, fetch my drafting thick parchment. We need to lay out the town grid before the refugees arrive.”