Accession No
2309
Brief Description
Soho type engineer’s slide rule, English, circa 1800
Origin
England
Maker
Class
calculating
Earliest Date
1800
Latest Date
1800
Inscription Date
Material
wood (boxwood); ivory; metal (brass)
Dimensions
length 267mm; breadth 35.5mm; thickness 6mm
Special Collection
Provenance
Purchased from Peter Delehar, 05/1977.
Inscription
Description Notes
Boxwood slide rule with ivory slide.
Obverse: lower half carries log slide rule. Double log scale on both stock and slide divided 1 - 10[0], numbered 1, 2, 3...1[0], 2[0]...10[0]; 1 - 2 subdivided to 0.02, 2 - 4 subdivided to 0.05, 4 - 10 subdivided to 0.1, 10 - 20 subdivided to 0.2, 20 - 40 subdivided to 0.5, 40 - 100 subdivided to 1. Second log scale divided 1 - 10, numbered by 1, 1 - 2 subdivided to 0.01, 2 - 4 subdivided to 0.02, 4 - 6 subdivided to 0.05, 6 - 10 subdivided to 0.1. Reverse of slide has log scale of sines, marked ‘S’, divided 1˚ - [90˚], numbered 1, 2, 3...10, 20...70, 1˚ - 10˚ subdivided to 10´, 10˚ - 20˚ subdivided to 30´, 20˚ - 30˚ subdivided to 1˚, 30˚ - 70˚ subdivided to 2˚, 70˚ - 80˚ subdivided to 5˚; log scale of tangents, marked ‘T’, divided 1˚ - 45˚, numbered 1, 2, 3...10, 20, 30, 40, 45, 1˚ - 10˚ subdivided to 10´, 10˚ - 20˚ subdivided to 30´, 20˚ - 45˚ subdivided to 1˚; scale of inches, marked ‘IN’, divided [0] - 10, numbered by 1, subdivided to 1/60. Upper half carries tables of design factors for size ratios of steam engines.
Reverse has tables of specific gravity, gauge points, conversion tables, etc.
One edge: scale of inches, divided [0] - [10.5], numbered by 1, subdivided to 1/8.
Other edge: decimal foot scale, divided [0] - [87], numbered by 10, subdivided to 1.
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:39561
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