Compass of proportions. France, XVII-XVIII century.

Compass of proportions. France, XVII-XVIII century.
Brass.
With the inscription "Beguinot les Cords a Paris".
One of similar characteristics and period is conserved in the Maritime Museum of Barcelona.
Measurements: 0,50 x 17 x 3 cm (closed).

Proportion compass, also known as pantograph or sector. This instrument of approximate calculation was used by sailors, artillerymen and engineers from the 17th century to the middle of the 19th century. It consists of two arms joined by a joint, allowing the angle between them to be adjusted. The arms are marked with radial scales that allow calculations based on proportions and similarity of triangles. It was used to perform multiplications, divisions, trigonometric calculations, among other applications. English models were usually made of bone with logarithmic scales, while continental models were made of brass. The proportion compass was popularized by Galileo Galilei and became an essential tool in various technical fields. Today, it is considered a historical piece of science and technology.