The sound that broke the vaulted chamber was not the muffled roar of sapper powder. It was the dry, sharp crack of overstressed granite giving up its structural bond, splitting down its centerline with the instantaneous violence of a lightning strike hitting a dry pine.
Above Jon Hale’s head, the great semicircular inner stone intake-arch that had carried the heavy burden of the Old Hill road for sixty years parted along its crown.
A jagged black fracture leaped across the central keystone, racing through the dressed voussoirs to the left and right springers in a single, devastating heartbeat. The lime mortar between the four-ton stones did not crumble into powder; it blew out horizontally under hundreds of tons of shearing load, spraying the flooded canal with a hail of white limestone shards that stung Jon’s face and tore through his wool sleeves.
“Get down!” Jon roared, throwing his shoulder against Alden Bram’s hip to force the mason toward the lower catwalk.
The master mason was already moving, his heavy boots skidding in the knee-deep mud, but forty years of working the quarry beds had left his joints thick and slow. Bram reached out to catch the twelve-foot spruce timber they had wedged beneath the lintel, hoping to stabilize the stone, but the mountain did not wait for carpentry.
