## Scientific Instrument Society 25th Anniversary Exhibition

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### 41 Early Gunter's Scale

*The Gunter’s Scale was mainly used in navigational calculations. I consider this two-foot, boxwood ruler to be the earliest known, dated example.*

*In 1623 Edmund Gunter (1581-1626) described his mariners cross staff and had a logarithmic ‘line of numbers’ marked on the staff. This evolved into the ubiquitous Gunter’s Scale, which continued to be made, with very little change, until the beginning of the nineteenth century. *

*It is marked with *Lea* (Leagues), *Rum* (Rhumbs), *Lon* (Line of Longitude), *Cho*[rds], *SR* (Sines of the Rhumbs), *TR* (Tangents of the Rhumbs), *Numb* (Numbers, a logarithmic line), *Sine*, *Tan*[gent], *Merid* (Meridian-Line), *EP* (equal parts) and a scale** of English inches. These scale**s were used with a pair of dividers to solve problems in navigation and trigonometry. It is stamped with what is probably the owner’s name, ‘Thomas Annand’ and the date ‘1683’.*

*See: E. Gunter, *Description and use of the Sector, Cross-staff and other Instruments, 1623.*(Note: although both instruments are illustrated, only the cross-staff is graduated with a logarithmic line).*

Collection: Peter Delehar, London

Objects lent by **Peter Delehar, London**:

08. Circular Slide Rule on a Snuff Box, by Hoyau, Paris, 1816

11. Reversible Circular Slide Rule, English, c.1840

25. Slide Rules - a Selection of the Original Pocket Calculators

26. Javal's Ophthalmic Slide Rule, by A. Cretes, Paris, c. 1875

27. Triangular Slide Rule with Four Sliders, by Elliott, London, c. 1870

28. Oil Calculation Slide Rule Designed by Forrest M. Towl, New York, c. 1889

29. Master Rule and Gauging Slide Rule, by Dring & Fage, London, 19th Century

30. Anderson Celluloid Gridiron Slide Rule, by Casella & Co, London, c. 1903

31. Slide Rule in a Drawing Scale, by J. Casartelli, Manchester, c. 1870

32. Circular Slide Rule, by Joseph Lamb, London, c. 1827

33. Roubicek Circular Slide Rule for Surveying, by Neuhöfer & Sohn, Vienna, c. 1870

34. Annular Slide Rule, by Elliott Brothers, London, c. 1875

36. Box Sextant with Integral Slide Rule, by Troughton & Simms, London, c. 1870