A discours of the variation of the cumpas, or magneticall needle. : Wherin is mathematically shewed, the maner of the obseruation, effectes, and application thereof,
A discourse by William Borough, printed in London in 1581 for Richard Ballard, treating the variation of the magnetic compass for navigators and mathematical practitioners. Its pictures are precise geometric diagrams of circles, chords and angles, a semicircular protractor-style instrument with graduated scale, and a small decorative strapwork border, offering a designer clean compass-and-protractor linework and ornamental band ideas.
