English School, (16th century). Medium: woodcut. Date: 1595. John Davis (c.1550-1605) was one of Elizabeth I's top navigators and explorers. 'A Seaman's Secrets' was a navigation manual. The Cross-staff, also known as Jacob's Staff, was a tool used in early celestial navigation. Inscribed "Are these all the rules that appertaine to the finding of the Poles height?" Provenance: Private Collection.