File:Backstaff.jpg

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"The back-staff, also known as the Davis quadrant (called a quadrant because it could measure up to 90º), was the first instrument specifically designed for finding latitude at sea. English explorer John Davis conceived the instrument while on a voyage to find the Northwest Passage and in 1595 described it in his book The Seamen’s Secrets."

Excerpt by Jeanne Willoz-Egnor from http://www.ion.org/museum/item_view.cfm?cid=6&scid=13&iid=31

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current20:30, 25 March 2011Thumbnail for version as of 20:30, 25 March 20111,024 × 819 (274 KB)Sean (talk | contribs)"The back-staff, also known as the Davis quadrant (called a quadrant because it could measure up to 90º), was the first instrument specifically designed for finding latitude at sea. English explorer John Davis conceived the instrument while on a voyage t
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