Three hours before mean low water, the western bypass trench stood ready. A channel forty feet wide, carved directly out of the native dark rock cliffs eighty years before, had been cleared of forty years of willow scrub, silt, and town debris by two hundred volunteer laborers working in six-hour shifts.
At the head of the channel stood the massive balance weight water gate designed by Renn Tal. Three twelve-inch timbers of seasoned white oak, heavy with forged iron straps and pinned through with two-inch drift bolts, rested in upright granite guides. Overhead, suspended from a heavy timber gallows-frame, hung a four-ton stone crib filled with quarry ballast, connected to the gate by four-inch braided hemp cables running through cast-iron pulley wheels.
Tomas Reed, Nessa Vale, and Renn Tal stood upon the running platform overlooking the intake race. A hundred feet away, behind a temporary cofferdam of timber piles and puddled clay, sixty feet of mountain river pressed against the stone face with huge, silent fury.
“This is the moment of truth, Master Tal,” Nessa said. She held her brass leveling staff steady against the stonework bridge pillar. Her sound horn was pressed against the bedrock. She listened to the deep, low, deep groan of the limestone strata under high-pressure tension.
Renn Tal took off his engineer’s glasses, wiped the river mist from the glass with a trembling thumb. Then it stepped to the trip-lever. From his coat pocket he drew his royal pension patent. A gold-trimmed thick parchment scroll granting him eight hundred silver crowns a year for life, signed by the country governor thirty-nine years before. Without a word, he struck a match against the stone, held the flame to the dry sheepskin. Then he watched the gold-leaf seal curl and blacken into ash.
“Thirty-nine years of comfortable silence,” Renn whispered. He dropped the burning parchment into the dark water below. “Let the river judge my building, not my silence.”
He seized the oak trip-lever with both hands and threw his weight downward. With a sharp, metal crack that echoed off the dark rock gorge, the iron dog-latches released. The four-ton stone balance weight dropped smoothly into its timber well. The three-ton oak water gate surged upward six feet in a single, fluid motion.
A wall of black mountain water struck the dark rock channel with the roar of an avalanche. A geyser of white spray erupted fifty feet into the night air, drenching the platform in freezing river mist. The torrent rushed into the western bypass trench, hugging the banked curve exactly as Nessa had surveyed. Its tremendous striking force faded away channeled into the deep dark rock stilling basin.
Down on the lower stone apron beside the second baffle pier, Mara Flint and four of her veteran wedge-men stood behind a breastwork of mortared granite blocks. They held long ash sounding-poles tipped with flat iron shoes. As the foaming crest of the trial bore hammered through the narrow throat where the old fish-market rubble had been cleared an hour earlier, the water boiled six feet up the dressed dark rock wall, throwing up chunks of waterlogged pine bark and black river peat.
“Check the scour on the east joint!” Nessa shouted through her speaking-trumpet, leaning far out over the wet timber rail while apprentice Olla held the tail of her oilskin coat.
Mara Flint drove her twelve-foot iron-shod pole straight down through the churning white water until the flat shoe rang solid against the bedrock doorstep. She held the shaking ash shaft against her leather apron for ten full seconds, reading the tremor of the current through her palms the way a miller reads the grind of a burr-stone. Then she raised her left fist above her head—three fingers extended, thumb closed. Clean rock bottom. Zero undermining of the lower mortar course.
On the running platform, Renn Tal gripped the wet oak guard-rail with both hands, his white hair plastered to his forehead by the freezing spray. For the first time since Tomas had met him in the cramped rooms of the lower town, the stoop in the old mage’s shoulders had vanished. He stared down at the four-ton balance weight crib sitting snug against its lower oak bumper-blocks in the dry well, then at the cast-iron pulley wheels spinning smoothly on their animal fat-greased bronze bearings.
“In Year One, Darven Holt swore before the Privy Council that no timber-and-stone gate could lift against a sixty-foot head without four hundred crowns of imported potion-made brass and a permanent ward-battery,” Renn said. His voice rose clear and bitter above the thunder of the chute. “Look at those pulley wheels, porter. Two hundredweight of pig-iron cast at the South Basin foundry, four tons of waste granite from the Old Flint spoil-heaps, and sixty deep-water lengths of honest tarred hemp braided by the rope-walkers at Reed Bank. Not a single human soul tied to the pins. It lifted six feet in four seconds.”
Tomas stood beside the main winch drum. His left forearm was tucked safely inside the oiled calfskin brace and wool sling. Meanwhile, his right hand rested on the iron pawl-lever. Through the thick oak planks of the platform, he could feel the deep, steady thrum of eight hundred cubic feet of water per second dropping away from the Hero Monument’s intake under-road drain. On the brass float-rod bolted to the eastern wing-wall, the painted white marker-bob was already sinking—half an inch, then a full inch, then two inches—as the impounded pool head bled sideways into the dark rock relief trench.
“Olla, give me the pressure reading on the monument drain tube under-road drain!” Tomas called down to the stonework steps where the young apprentice knelt beside the liquid silver U-tube gauge connected to the main vault pipe.
Olla held her animal fat lantern close to the glass tube, shielding the flame from the driving mist with her wool cap. “Sixty-one pounds to the square inch and falling, Master Reed! It has dropped nineteen pounds since the gate rose! The back-surge in the main intake race has already broken!”
Below the stilling basin. There, the dark rock trench widened into the three-mile earthwork canal leading toward the South Holding Polders, Lani Moss’s signalman swung a green bullseye lantern three times from the top of the turf levee. The trial wave had passed the first clay weir without overtopping the bank by a single finger-breadth. The dry reeds along the polder ditch were drinking the mountain flood exactly as the eighty-year-old stonework builders had intended before the guild walled up the entrance.
Renn Tal reached out with one wet, gnarled hand and touched the cold iron strap of the raised water gate. “Lock the upper ratchet pawls into the third tooth, Tomas,” the old engineer said quietly. “Even if Holt’s hired blades bring a battering ram to this platform before dawn, they can’t drop a three-ton oak gate while the balance weight crib is pinned at the bottom of the well. The river has its road back.”
Tomas threw his weight against the iron pawl-lever with his right arm. He drove the heavy forged tooth home into the ratchet wheel with a solid, ringing clank. Then he dropped the safety cotter pin through the iron eye. With his pocket pencil, he logged the exact pawl setting and the twenty-pound drop in under-road drain pressure across the back of Renn Tal’s signed check ticket, sealing the building transfer in the carrier’s book before the spray could wet the paper.
Nessa leaned over the low roof wall, her eyes fixed on the tuned brass markers set into the channel wall. “Speed is nine point four feet per second! Bending on the guide timbers is less than two hundredths of an inch! The bypass is holding! The high-pressure grade line is stable! We can take the full river discharge at low tide!”