At four in the afternoon, Corvin returned to the cooperage carrying an oblong tin map-case sealed with green cord. His woolen cape was soaked with rain, but his eyes were blazing behind his round glasses.
‘I found it,’ Corvin whispered, closing the heavy oak door and throwing the bolt. ‘Varo Nenn helped me unlock the private chest in Sub-Basement Two. It was buried under forty years of holy treatises on river spirits.’
He drew out Roll Fourteen-A—an unilluminated working draft on heavy sheepskin thick parchment, dated four years prior. Across the center of the drawing, the emergency bypass was clearly marked with an opening threshold of sixty pounds of pressure. A safe, conservative pressure that would have vented any surge long before the baked-clay under-road drains could fail.
Across that original figure, drawn in sharp, aggressive red ink, was a thick level line. Above the cancellation, written in Master Davin Sorell’s clear, spiky hand, were the new numerals: ‘bone-crushing pressure.’ Beside the change was a marginal note written in Sorell’s own Latin script. ‘Threshold raised to prevent premature venting of pulled out ringing energy during commercial test cycles.’
Pella read the Latin note twice, her breath catching in her throat. ‘He didn’t make an exact error. He deliberately raised the threshold because venting the surge would reduce the energy output of his test. He gambled forty thousand lives so his machine would look more powerful before the Senate.’
