Walter Shawlee, the Sovereign of Slide Rules, Is Dead at 73

For about 350 years, humanity’s most innovative hand-held computer was something called a slide rule. As typewriters once symbolized the writer, slide rules symbolized the engineer.

These analog calculators came in metal, wood, plastic and even bamboo, and they could be found all over the world. Their functions included computing higher-order multiplications, exponents and logarithms, among other mathematical operations. They were usually long and rectangular with a retractable middle segment, and they featured dense fields of letters, lines and numbers stacked on top of one another.

They looked almost comically abstruse, as if they might be used as paddles in the hazing rituals of a math fraternity.

Non-nerds struggled to make sense of them. Then, in the early 1970s, lightweight electronic calculators became widely available. The market for slide rules collapsed, and manufacturing of new devices essentially ceased.

One day, about 20 years later, a middle-aged avionics engineer by the name of Walter Shawlee was looking through a drawer at his home in Kelowna, a midsize city in British Columbia, when he happened upon his old slide rule from high school.