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27 Triangular Slide Rule

image of Triangular Slide Rule

This boxwood slide rule was made for general scientific calculations and is signed ‘Elliott 449 Strand London’. The firm of Elliott Brothers were trading at this address between 1864 and 1886. The complexity of producing a stock of triangular cross section must have been unnecessarily formidable, but what is even more strange is that the triangular cardboard box contains a fourth slide! It would have been much easier and cheaper to make a four-sided slide rule, particularly because instruments of this format already existed. One can only speculate why such an experienced and well-known firm did not advise the inventor to go back to the drawing board.

Frederick Henry Elliott (1819-73) and his bother Charles Alfred Elliott (1822-77) usually signed their instruments ‘Elliott Bros.’, however this slide rule is simply signed Elliott and it is conjecture that one of the brothers devised it and was happy to have his name on it, but his brother did not want to have his name associated with such a silly idea; but which brother? They were known to make one-off instruments for customers, but if this is the case here, then I am surprised they did not advise them of the folly.

English c.1870.

Collection: Peter Delehar, London

For a detailed discussion of the Elliot family of instrument makers see:
Bulletin of the Scientific Instrument Society, No. 36 March 1993, pp. 2-11.

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

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

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

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