The Otis King and Fuller slide rules are similar in appearance as both use a helical logarithmic scale.
The larger Fuller’s Spiral Slide Rule is a total 33cm in length excluding the handle and boasts a 12.5 m long scale wrapped helically around its main body. Designed by George Fuller in 1878, 14000 were produced by W.F. Stanley. It uses one logarithmic scale and two cursors in the form of brass fingers to allow multiplication and division accurate to four or sometimes five figures. The inner scale provides logarithms and sines. It was used by S.G. Lusby, who was appointed as an assistant lecturer in 1912.
Its smaller companion was made in the early 1900’s, estimated 1910, with a scale approximately 170 cm long. The inventor of this piece, Otis Carter Formby King, lived 1876 to 1944 and joined a manufacturing company, Carbic Ltd, in London for the production of the Otis King Calculator. The long scale gave better resolution, although the accuracy was compromised somewhat by misprints and warping of the scale as it was wrapped. Still, it was capable of an accuracy of one part in two thousand.
To use it, one would rotate the outermost and innermost cylinders, selecting the required numbers to be multiplied or divided on the logarithmic scales. Successive multiplication and division could be combined in 1 movement.
Both types of cylindrical slide rule were used in various science and mathematical backgrounds, education, banking, and even in tax return calculations.
This item is part of the UQ Physics Museum Good Old days of Calculation Tour
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