Bras sector, 1623.
© Science Museum / Science & Society Picture Library
A bras sector (Gunter's pattern) made by Elias Allen. Allen made the sector to the design of Edmund Gunter who published a description of it in the same year. Sectors were used from the end of the 16th century until the mid 19th for calculations involving proportion. This example contains logarithmic and trigonometric lines and lines used in drawing and calculations of area and volume.