The Description and Use of the Sector
The Description and Use of the Sector is a 1624 English treatise by Edmund Gunter, written as a practical manual for navigators and surveyors on the sector, a hand-held calculating instrument. Its pictures are geometric diagrams with radiating lines, numbered hour and compass markers, and lettered points, showing how dials and rhumb lines were laid out. A designer might take from them the clean radial structure of line-based instructional plates, with labelled rays fanning from a central point.
