Kezra stood on the locust-wood staging deck at the one-hundred-and-twenty-eight-pace landing. She unclipped her brass sounding rod and assembled its three linked sections with crisp, practiced twists. The threads seated home with a sharp metal click that rang through the quiet stone gallery.
“Before we go an inch deeper, Voss,” Kezra said, “we verify the Quarter datum.”
She knelt on the staging deck and set the brass-shod tip of the rod into the center benchmark socket recessed into the granite floor. She lifted the rawhide mallet. She struck three steady, measured blows against the rod’s upper collar.
Ting. Ting. Ting.
The sound return was instant, clear, and bell-like. Her intact right ear caught a clean, single-hum ring that held for four seconds before decaying into silence. Meanwhile, her fingertips against the rod felt a sharp, elastic rebound devoid of chatter or flutter. The sound wave traveled through the stone at about five thousand five hundred yards per second, returning from the surrounding boundary faces with textbook symmetry. From the delay and hum, Kezra calculated the bulk modulus and shear speed of the rock mass. She confirmed that the elastic properties of the pluton were fully uniform across the entire parcel.
