The fourth watch brought an obstacle that could not be cleared by the shovel alone.
At a depth of twelve feet within the silt basin, the blade of Qiao Ming’s iron spade jarred against an unmoving timber that spanned thirty arm-lengths across the drainage channel. The wood was black as coal, dense as pig-iron, and thick as an ox’s flank, wedged diagonally between two dark rock pilasters that supported the lower arch of Sluice-Gate Nine.
The current from the upper drain tubes had packed thousands of tons of gravel behind this timber, forming a solid underwater dam that held back twenty feet of stale sludge. Until this beam was cut and pulled out, no further progress could be made toward the foundation drain.
Qiao Ming knelt in the freezing slurry, clearing the muck from the wood with his bare hands. His fingers traced the surface of the timber. It wasn’t rotting driftwood, but a massive square-hewn baulk of sky cedar, its grain so dense and pine-scented that four hundred years of flooding in saltwater had failed to soften its fibers.
He took his bronze scratch-awl from his apron and struck the timber. The tool bounced off the surface with a high, metal chime, leaving barely a pale scratch in the black bark.
