Determining one’s position at sea required expertise in using many complex instruments, including celestial, magnetic, and mechanical devices.
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John Davis, captain of three Arctic voyages, combined mathematical skill with practical nautical experience. In 1594 he invented the “Davis Staff,” an important instrument which would be widely used for measuring the altitude of the sun. Davis reversed the traditional cross-staff, so that the sailor measured the shadow the sun cast on the staff rather than staring directly at the sun itself. This image in Davis’s book of maritime instruction represents a fairly simple early version of the staff, which would be refined and used into the eighteenth century.
Instruments, cont'd
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Mariner's astrolabe. Replica of an instrument from Valencia, ca. 16th-17th century
Thomas Blundeville. M. Blundevile his exercises. London, 1606
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