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Dolland's Sector

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A sector rule, originally invented by Galileo and then developed by the English mathematician Edmund Gunter who added the crucial logarithmic scales in about 1624. This allows the sector to be used as a straight logarithmic rule, or more importantly, it can be used in conjunction with a pair of dividers to make trigonometric calculations required for navigation at sea. This fine example signed by the maker, Dolland of London. Ivory with an engraved and signed white metal hinge.

 

English circa 1780.

 

12 inches when open; this sector will not close tightly. (See the photographs).

Item Code: 3301

£ 345

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