Accession No
1013
Brief Description
navigational slide rule, English, 18th C or 19th C
Origin
England
Maker
Class
calculating
Earliest Date
1700
Latest Date
1900
Inscription Date
Material
wood (boxwood); metal (brass)
Dimensions
length 315mm; breadth 42mm; thickness 7mm
Special Collection
Provenance
On loan from Trinity College, University of Cambridge from 1951.
Inscription
Description Notes
Boxwood slide rule with brass bound ends.
Face A: upper part of stock carries scale of inches divided [0] - [12], numbered by 1, subdivided to 0.1. Also double radius log scale, marked ‘N’, divided 1 - 10[0], numbered 1, 2...1[0], 12, 2[0], 3[0]...10[0]. Slide carries identical scale, also marked ‘N’, on upper edge; lower edge carries scale of rumbs (?), marked ‘SR’, divided [0.25] - 8, numbered by 1, 0.25 - 7 subdivided to 0.25. Lower part of stock carries another scale of numbers, identical to the first two; also a decimal foot scale divided [0] - [100], numbered by 10, subdivided to 1.
Face B: upper part of stock carries scale marked ‘EP’ (equal parts), divided [10] - 0 - 110, numbered by 10, subdivided to 0.5. Also scale marked ‘M’ (meridional parts), divided [0] - [76˚], numbered by 10˚, subdivided to 1˚. Also scale marked ‘T’ (tangents), divided [40´] - 45˚ and back to 80˚, numbered 1˚, 2˚...10˚, 20˚...40˚, 45˚, 50˚, 60˚...80˚. Slide carries scale of tangents marked ‘T’, identical to the previous one. Also scale of sines, marked ‘S’, divided [40´] - 90˚, numbered 1, 2...10, 20...90. Lower part of stock carries indentical scale of sines, marked ‘S’. Also four further scales: first marked ‘Leag’ (leagues), divided [10] - 0 - 100, numbered by 10, first 10 subdivided to 1; second marked ‘C’ (chords), divided 0 - 90˚, numbered by 10˚, subdivided to 1˚ (inlet brass point at 0); third marked ‘M. Lon’, divided 0 - 60, numbered by 10, subdivided to 1 (with inlet brass point at 60); fourth scale marked ‘R’ (rumbs), divided 0 - 8, numbered by 1, subdivided to 0.25.
Condition good; complete.
References
Events
Description
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.
FM:42526
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