Accession No
0104
Brief Description
Otis King’s Pocket Calculator, cylindrical slide rule, by Carbic Ltd, mid-20th Century
Origin
England; London; 51 Holborn Viaduct
Maker
Carbic Ltd.
Class
calculating
Earliest Date
1900
Latest Date
1950
Inscription Date
Material
metal (white metal, brass); paper; wood; hide (leather); cloth (velvet, silk)
Dimensions
length closed 165mm; diameter 30mm box length 178mm; breadth 55mm; height 38mm
Special Collection
Cavendish Collection?
Provenance
Hutchinson collection
Inscription
‘OTIS KING’S POCKET CALCULATOR.’ (instrument)
‘COPYRIGHT.’ (instrument)
‘SCALE NO 423.’ (instrument)
‘PATENTEES & SOLE MANUFACTURERS; CARBIC LIMITED, 51 HOLBORN VIADUCT, LONDON, E.C.1.’ (instrument)
‘SCALE NO 414. COPYRIGHT.’ (instrument)
‘OTIS KING’S PATENT NO 183723.’ (instrument)
‘Otis King’s
PATENT
CALCULATOR’
Patentees & Sole Manufacturers,
Carbic Limited,
51, Holborn Viaduct, London, E.C.1.’ (inside lid of case)
Description Notes
Otis King’s Pocket Calculator, cylindrical pocket slide rule with helical scales, by Carbic Ltd, mid 20th C.
White metal cylindrical handle surmounted by cylinder with helical scale on black paper. Cylindrical draw tube with similar scale and metal cursor with indices at top and bottom. Knurled white metal top with suspension loop.
Leather-covered wooden box lined with white silk and blue velvet (very faded); brass hinges and press fastener.
Condition good; complete
References
Mikey McGovern; 'Pocket calculating devices'; Explore Whipple Collections online article; Whipple Museum of the History of Science; University of Cambridge: https://www.whipplemuseum.cam.ac.uk/explore-whipple-collections/calculating-devices/pocket-calculating-devices
Events
Description
This is a variation on the type of slide rule most common in our displays, the scale for this kind of rule was developed during the late 17th century, this is it’s most advanced use, and the Otis King model of slide rule was popular due to its portability.
Developed during the seventeenth century, the modern slide rule is based upon the design by William Oughtred (circa 1630). It is one of many calculation devices that is based on the logarithmic scale, a calculation method invented in 1614 by John Napier.
Before the rise of the pocket electronic calculator in the 1970s, the slide rule was the most common tool for calculation used in science and engineering. It was used for multiplication and division, and in some cases also for ‘scientific’ functions like trigonometry, roots and logs, but not usually for addition and subtraction.
A logarithm transforms the operations of multiplication and division to addition and subtraction according to the rules log(xy) = log(x) + log(y) and log(x/y) = log(x) - log(y). The slide rule places movable logarithmic scales side by side so that the logarithms of two numbers can be easily added or subtracted from one another. This much simplifies the alternative process of looking up logs in a table, thus greatly simplifying otherwise challenging multiplications and divisions. To multiply, for example, you place the start of the second scale at the log of the first number you are multiplying, then find the log of the second number you are multiplying on the second scale, and see what number it is next to on the first scale.
Cylindrical slide rules allow calculations to be done that would otherwise require a linear slide rule of many times its length.
FM:42475
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