Ada and Pella explain the ‘pressure echo’ technique accurately to Korr Var, Corvin Hest, and the neighborhood crew: it detects trapped air pockets through touched pipes by sound rebound, and can’t read every buried line. She stood inside the washroom workbench around a six-foot test section of glazed terracotta drain-pipe. Ada Morland and Senior Engineer Korr Var set a brass-headed sounding hammer, a pocket stopwatch, and Ada’s wooden mechanic’s stethoscope where the lantern light fell cleanest across the work surface. Meanwhile, Junior Inspector Corvin Hest and Pella Rook checked the entry under the heading of How the Pressure Echo Actually Works.
The technical core of how the pressure echo actually works needed demonstrating how tapping a water-filled pipe produces a crisp metal ring where the water is solid. But returns a hollow, delayed double-thud where a pocket of trapped marsh gas or air cushions the wave. Throughout this phase of the ballad-seller’s exaggeration and the flood of merchant requests, the crew held fast to triage discipline over public spectacle. Every brass fitting, every stitched seam. Every thirty-minute lunch crossing had to answer to physical measurement rather than guild politics.
“People in the lane were saying I can lay my palm on a cobblestone and see every buried drain under Lathmere like an owl seeing mice in a barn,” Ada said, placing the wooden ear-piece of her mechanic’s stethoscope against Korr Var’s palm. “Listen for yourself, Engineer Var: my pressure-echo sensitivity only travels along a nonstop pipe wall that I’m physically…
