Name and Model Number  Gunter Rule, Sliding 
Country of Origin  England 
Date of Manufacture  c. 1800 
Front Scales  Inch N [ N N ] SR Mer E*P 
Back Scales  M:Lon Cho Sin [ Sin Tan ] Tan Sin Tan 
Scale Length  28 cm 
Type of Rule  Slide Rule 
Construction  Open frame, 30.5cm long slide rule. Two sided boxwood with brass end posts, no adjustment, and no cursor. Cursor not needed. 
Area of Use  Other 
Comment  For navigation & mathematics. The N scales on this slide rule are equivalent to A & B scales. This sliding Gunter is divided on both sides with logarithmic and trigonometric scales, some of which were designed specifically for navigation at sea. The "Sliding Gunter" was designed to supersede the common "Gunter Rule", which required dividers to calculate. The scale arrangement has been attributed to John Robertson, c. 1770s. This Gunter rule can be used to multiply, divide, and for proportional and plane trigonometry calculations. Its principal use was for navigation. Given the "Course" and "Distance", the navigation scales on the sliding Gunter rule could be used to calculate the difference in "Latitude" and "Departure" from one point to another. Undated and unsigned, this example could date to c. 1800.

Rarity  RRR 
Donor  Collection of Ed Chamberlain 
Match Number  370

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