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11 Reversible Slide Rule

image of Reversible Slide Rule

It surprises me that neither the inventor nor maker of this very unusual circular brass slide rule have their names engraved on it.

The stock, slider and alidade fit on a central pin; a similar manner in which the components of an astrolabe are held together. A clip on the alidade, the chamfered edges of which act as a cursor, engage with a groove on the pin and hold the components together. This ingenious device enables the central disc to be reversed. The bevelled front face of the stock has a double line (B) and the reverse a single line (D). The slider has on one face an inner triple radius line (E) and an outer double radius line (C). The reverse has inner double line (A) and an outer triple radius line (E). Only the inner graduations can be read against the bevelled edge.

English ca.1840

Collection: Peter Delehar, London

Objects lent by Peter Delehar, London:

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

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

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

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