The effect of the balance weight’s release on the high-pressure shape of Sluice Twelve was instant and violent.
Four tons of cast iron fell forty feet to the bottom of its cushion well. Then, the four-inch link chains running over the crest sprockets snapped taut with a ringing chime that echoed across the entire two-mile face of the Diverter. The sixty-ton outward gate leaf, which had been jammed four inches crooked for seventy-two hours, was suddenly subjected to balanced upright counter-leverage.
High up in the discharge water chute behind Pier Twelve, the massive outward gate shuddered. With a bone-shaking, grinding screech of bronze against granite—SKRRR-THUMP—the gate leaf dropped four inches into its dressed bedrock doorstep.
The gate was seated.
Instantly, the total rooster-tail of brown water and gravel that had been erupting from beneath the crooked doorstep collapsed. The seventy-foot geyser of spray vanished from the lower tailrace, replaced by a flat, uniform boil of white water that discharged cleanly into the center of the river bed.
Even more dramatic was the sound.
The terrifying, high-pitched whistle of bubbling blast that had been screaming from the stonework of Pier Seven since midnight suddenly lost its ringing hum. The pitch dropped from a piercing scream to a dull, heavy, deep-throated rumble. The sound of water flowing through designed high-pressure channels rather than tearing through load-bearing stone.
