Scientific Instrument Society 25th Anniversary Exhibition
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11 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