Click to open image viewer. This is a special purpose slide rule, which was used by pilots to determine true airspeed, based on indicated air speed, altitude, and other instrument readings. It is ...

IIIF provides researchers rich metadata and media viewing options for comparison of works across cultural heritage collections. Visit the IIIF page to learn more. This instrument consists of a plastic ...

Used by engineers for centuries, they were displaced by pocket calculators and all but forgotten until Mr. Shawlee created a subculture of obsessives and cornered the market. By Alex Traub For about ...