Beyond the bronze portal of the navigators lay the high-pressure artery of the Ashen Epoch: Entry hall 670, the Grand Pipe of Siphoned Steam. Here, the underground space narrowed into a huge circular tunnel eighteen arm-lengths in width, lined entirely with riveted boiler plates three inches thick and lagged with hardened mats of glass-fused asbestos.
This channel had once carried white-hot steam at two crushing deep-sea pressure from the deep earth-heat chimney pipes of the world-size mantle directly into the high spreading turbines of the central castle walls. Now, it was a silent, echo-choked hall, sloping gently downward into the dark at an inclination of three degrees.
Qiao Ming walked along the invert of the pipe, his bare calloused feet gripping the curved iron plates. The bottom of the channel was dry, but scored with long, parallel gouges where heavy iron check sledges had once been dragged along the metal. The air here was strangely light and warm, carrying the sharp, bitter-salt smell of dry lime and rotten-egg rock.
Behind him, Yan Zhiqiu walked with one hand resting against the riveted seam of the pipe wall. The iron was noticeably warm to the touch—not hot enough to burn flesh, but holding a steady, blood-like warmth conducted upward through six miles of solid dark rock from the magma trenches below.
