The fourth arch of the eastern aqueduct in the Great Silt Plaza had been weeping black salt water for nineteen days.
It was a huge structure. A half-round barrel-arch forty arm-lengths across, built from six-ton arch stones of yellow banded limestone that supported the weight of the upper freshwater channels. During the violent water-pressure surges of Season 17, the settling of the lower foundations had driven a hairline slanted shear across three central arch stones. A steady, freezing drip of bitter-salt water had been eroding the lime mortar, dissolving the joint until the gap was wide enough to slip a carpenter’s hand between the stones. Mortal refugees sheltering below had braced the arch with rotten pine spars. But every man who looked up at the sagging keystone knew that if the arch dropped, forty thousand tons of stonework would collapse into the crowded third terrace.
Qiao Ming and Yan Zhiqiu stood at the base of the damaged pier. Qiao Ming ran his calloused index finger along the edge of the fracture, feeling the cold, greasy film of dissolved calcium sulfate. He unfolded his brass measuring tongs and measured the gap at three distinct depths: four inches at the intrados, three inches at the core, and two inches at the extrados.
