Wilhelm Schickard

Wilhelm Schickard taught Hebrew and astronomy in Germany until his death in 1635, but his real mark surfaced only in the 1950s when a Kepler biographer found two lost letters from 1623 and 1624 describing a calculating clock. The drawings had actually been published repeatedly since 1718, though no one connected them to the calculator story. Schickard's design paired an adding machine with a rotated Napier's bones system for multiplication — the first known hybrid of its kind — but the single-tooth carry mechanism didn't work reliably and the prototype was never finished. Later 17th-century in…