Old school vernier calipers served engineers and machinists well for a long time — and did a perfectly good job. Digital models then came along and were easier to read. They now rule the roost, ...

A protractor is used to draw and measure angles. An angle is the amount of turn between two lines. Angles are measured in degrees with the symbol °. Angles can be labelled with 3 letters (eg DEF) to ...

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 semicircular brass protractor 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. In the early 20th century, some ...

If you enjoyed this article, I’d like to ask for your support. Scientific American has served as an advocate for science and industry for 180 years, and right now may be the most critical moment in ...