The physical reality of an airtight stone chamber under negative air pressure is something that neither philosophers nor aldermen ever think about. To the scholars in the libraries of Crown-Reach, air was an invisible, weightless element that existed everywhere without cost. But to Tomas Reed, who had spent his youth unloading grain barges in high-pressure canal locks, air was a fluid mass that possessed thickness, driving force, and crushing physical power.
Inside Bay Fourteen, three adults had burned up over two hundred cubic feet of oxygen in two hours. Meanwhile, their whale-oil lantern and spirit-lamp had burned another three hundred. The burning of carbon and the absorption of moisture by five hundred crates of dry parchment had pulled the internal pressure down to nearly two inches of liquid silver below the surrounding air of the city above. Across the four copper flapper plates in the ceiling, that negative differential exerted over fourteen hundred pounds of total inward suction. He locked the copper plates against their animal fat-soaked leather rubber rings as though they had been brazed shut with molten lead.
“If Sile trips the balance weight while the empty pocket is locked,” Tomas called out toward the eastern pier, his voice calm and deliberate, “the eight-hundred-pound weight won’t be able to overcome the sky suction on the flappers. The winch cable will snap under the shock load. Or the brass cam will shear its shear-pin.”
