Under the sheltered arch of the Canal Lock Keeper’s shed, thirty paces from the roaring Sluice House, Renn Tal spread a yellowed linen drafting sheet across the top of an overturned salt-pork barrel.
The drawing was a sectional height of Central Steam Sluice Number One, drawn thirty years earlier in Tal’s own careful hand. Just then, he was Chief Mechanical Draughtsman for the Municipal Public Works Board.
Tomas Reed, Nessa Vale, and Sile Rook gathered close, their breath pluming white as they shielded the fragile drafting cloth from the sleet with their canvas coats.
“Listen to me, Tomas,” Tal said. His index finger shook as he tapped the ink drawing of a huge upright cast-iron metal tube. “This is the main spreading chest—the Great Sluice Header. It sits sixty feet long, five feet in width, cast from muck iron with three-quarter-inch walls. Six steam mains enter from the fire boilers on the east. Four delivery mains exit to the rolling mills and the pumping stations on the west.”
Tal traced an upright shaft running from the top of the header through the upper floorboards.
“Here is the safety bypass,” Tal continued. His voice shook with the urgency of a dying man. “It’s a forty-inch balanced flapper valve, held shut during normal operation by a compound lever linked to an eight-hundred-pound cast-iron balance weight suspended from the ceiling roof beams. If the pressure exceeds ninety-five pounds, the steam should overcome the balance weight and blow the valve open, venting the entire…
