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36 Slide Rule on a Box Sextant

image of Slide Rule on a Box Sextant

The box sextant is a convenient and easily portable instrument used by civil and military engineers to measure the angle between two terrestrial features by means of double reflection. The mirrors are housed within the box, and a gear, operated by a knob on the top plate, moves the index arm. The cylindrical cover screws onto the base and acts as a handle. It is signed next to the arc ‘Troughton & Simms, London’ and was made about 1870.

What makes this box sextant possibly unique is that fixed to the top of the lid, and having its own cover, is a circular scientific slide rule made of electrum.

When the noted instrument maker Edward Troughton (1756-1835) retired in 1826, he took into partnership William Simms (1793-1860).

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

41. 2ft Gunter Rule, owned by Thomas Annand, English, 1683

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