The eight bronze deadbolts of the Great Iron Arch had become one with the living bedrock.
Qiao Ming walked the upright outer edge of the iron gate, his horn lantern held high to light up the sixteen-foot guide-tracks. He carried a block of pure sheep fat and an oily rag of boiled flax. At each deadbolt, he rubbed the grease deep into the wood slot joints, ensuring that the cold metal did not gall or seize under the huge deep water pressure bearing down upon the outside face.
The gate was a building masterpiece of the First Dynasty. Eighteen hundred tons of forged bog-iron, alloyed with nickel and cold-hammered copper, hung suspended in granite guide-tracks sixty feet high. Under the load of eighty deep-water lengths of outer deep-sea salt water, the iron did not bow. Its segmental curve passed ninety-eight percent of the level thrust directly into the four-hundred-foot dark rock stone props flanking the archway.
He brought his Folded brass star-compass to the central bending gauge mounted at mid-span.
The hair-width needle showed that the centerline bending of the gate under peak moon-tide line-up load was less than one-thousandth of a tiny fraction of an inch. A shifted weight so tiny that it fell below the measurement error of the instrument. The arch was as unbending as the center of the earth.
