another matter. A tremor had settled into his fingers over the preceding years, sometimes mild enough to disappear when he rested them on the bench and sometimes severe enough to turn the simplest precise movement into an argument between his mind and his body.
There had been a time when Silas could rebuild a pump while talking about the weather and never look twice at a measurement. He still knew what needed to be done, sometimes more clearly than the younger mechanics who stopped by to ask his opinion, but the drill no longer remained perfectly centered when he held it. He had once ruined a good component trying to convince himself the tremor would settle if he concentrated hard enough. After that day, he stopped pretending that knowing how to do a job was the same as still being able to do it safely.
Jonah had grown up in the shop, first sitting under the workbench with wooden blocks to play with, then holding a flashlight, then handing his grandfather the correct wrench without having to be asked twice. By the time he was twelve, he knew which tools belonged in which drawer, and by fourteen he could recognize a failing bearing from the rough change in its sound. Silas never called these things lessons, but they were. He taught the way old mechanics often do, by noticing what a boy was looking at and asking whether the boy understood why it mattered.
The idea of practicing on broken castings had begun the autumn before, shortly after Dale's hydraulic housing failed. Jonah had asked why a fracture meant replacing the entire part if most of the surrounding iron still looked sound. Silas told him there were repairs that worked and repairs that merely delayed the failure, and that knowing the difference took more than enthusiasm. Then he went to a drawer, removed several samples of mechanical repair pins, and explained that certain cast-iron fractures could be closed and reinforced without simply heating the whole damaged section and hoping a weld did not create more trouble.
It sounded almost unbelievable to Jonah. To his eyes, a cracked engine block was an object permanently divided from itself, as final as a broken plate. Silas shook his head and reminded him that iron behaved according to stresses, temperatures, shapes, and constraints whether people understood those things or not. "The metal doesn't know if you're rich or poor," he said. "And it doesn't care how badly you need the repair to work. It only answers to what you actually do to it."