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Description: | NAVIGATION SCALE / BY B. DONN
This wooden rule is known as a Gunter scale or Gunter rule and has scales on each face to help with navigational calculations. The scales on the front include one in inches, diagonal scales that allow a pair of dividers to be set to an exact length, and a gunnery scale. Those on the back include sines and tangents. The maker's name is inscribed above the scale of inches as 'ACKERMANN & Co 96 STRAND'. The firm was working from this address in about 1850. A second inscription on the front reads 'NAVIGATION SCALE BY B. DONN', indicating that this was Benjamin Donn's improved version of the Gunter scale, which he described in a pamphlet in 1772. Donn (1729?98) was a teacher at a Mathematical School set up by his father in Bideford, Devon, before establishing his own Mathematical Academy in Bristol.
As improved by Benjamin Donn of Bristol in 1764 and 1772.
Standard scale arrangement except one change on back (NUM scale just called NUMBERS)
See O. van Poelje, 'The Navigation Scale, Improved by B. Donn', Journal of the Oughtred Society, 14 no. 2 (2005), pp. 36-42 | Publisher: | "http://collections.rmg.co.uk/" | Subjects: | Trigonometric functions Gunter rule Gunters' scales | Source: | Royal Museums Greenwich | Identifier: | http://collections.rmg.co.uk/collections... | Go to resource |
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