When the record for Alternating Waves of Underground Heat was opened in Ventilation Shaft #3 with its cast-iron grate lifted onto wooden chocks, Imran Bell directed everyone’s attention to a tuned silk-thread draft indicator tied to the end of Renn Vos’s six-foot ash rod alongside a maximum-minimum liquid silver bulb. By lowering a heat gauge and silk-thread wind vane into the shaft, Imran proves the beetles are following alternating twelve-minute waves of underground heat pulsing from the upper hill. Beside them, Pella Rook, Tavi, and Senior Engineer Korr Var double-checked the practical tolerances that governed the morning’s task.
The technical core of alternating waves of underground heat needed timing the twelve-minute periodic back-and-forth swing between hot upward exhaust puffs (74.5°F) and cool downward intake draws (59.0°F) inside the brick riser. Throughout this phase of the systematic cellar-to-cellar mapping of the lantern beetle colony, the crew held fast to reading living shifted weight as a heat map of the hidden trunk. Every brass fitting, every stitched seam. Every thirty-minute lunch crossing had to answer to physical measurement rather than guild politics.
“Watch the white silk thread on the end of the ash rod, Engineer Var,” Imran said. He held his pocket stopwatch beside the open brick mouth of the shaft. “For seven minutes the thread blows straight up toward our faces and the heat gauge climbs to seventy-four degrees. Then for five minutes the pressure drops, the thread sucks downward. The beetles halt on the upright mortar joints.”
