The solution to the sound blind spot was solved by veteran ferry watchwoman Hesta. She climbed to the ridge-pole of Sister Merrow’s three-story slate laundry roof. She held a twelve-foot pine pole fitted with two large flags of heavy fulled wool. One dyed bright madder red, the other bleached flour-white.
From the laundry roof, Hesta had a clear line of sight across the entire Lower Ward. She could look down into Miller Tom’s mill yard, across the Ferry Turning Basin, and along the full length of the Fish Street levee.
Pella blew her whistle in the noisy mill race. Then, young Tavi on the ground flashed an oil lantern toward the roof. Instantly, Hesta swept the red flag horizontally across the gray sky in two sharp, distinct arcs. In the mill yard, forty paces away, Miller Tom saw the red sweep from his meal floor window. He pulled the brake lever. Then he halted the stones in five seconds flat.
‘Visual semaphore established!’ Pella reported, laughing with relief as she watched the red flag cut through the drizzle. ‘When the river roars so loud you can’t hear the church bells, Hesta’s red flag will tell the city when to stop.’
