Accession No

0711

Brief Description

slide rule, by Troughton and Simms, English, 19th Century

Origin

England; London

Maker

Troughton and Simms

Class

calculating

Earliest Date

1800

Latest Date

1900

Inscription Date

Material

wood (boxwood); metal (brass)

Dimensions

length 612mm; breadth 41mm; thickness 7mm

Special Collection

Robert Whipple collection

Provenance

Purchased by Robert Stewart Whipple from T.H. Court on 02/03/1933.

Inscription

‘TROUGHTON & SIMMS . LONDON .’ (one edge)

Description Notes

Boxwood slide rule with ends bound in brass; two slides.
Obverse: upper section of stock has logarithmic scale marked ‘A’ divided 1 - 1[0], numbered by 1; 1 - 2 subdivided to 0.005, 2 - 5 subdivided to 0.01, 5 - 10 subdivided to 0.02. Middle section of stock has two logarithmic scales, one as A, the other an inverted version of A, marked ‘D’. Lower part of stock has logarithmic scale divided 1 - 10[0], numbered 1, 2, 3...1[0], 2[0], 3[0]...10[0]; 1 - 2 subdivided to 0.02, 2 - 7 subdivided to 0.05, 7 - 10 subdivided to 0.1, 10 - 20 subdivided to 0.2, 20 - 70 subdivided to 0.5, 70 - 100 subdivided to 1. Upper silde has two scales marked ‘B’ and ‘C’ both divided [10] - 100, numbered 2[0], 30, 40...100. ‘B’: 10 - 20 subdivided to 0.05; 20 - 50 subdivided to 0.1; 50 - 100 subdivided to 0.2. ‘C’: 10 - 20 subdivided to 0.1; 20 - 50 subdivided to 0.2; 50 - 100 subdivided to 0.5. Lower slide hastwo scales divided 1 - [10], numbered by 1; upper scale 1 - 2 subdivided to 0.005, 2 - 5 subdivided to 0.01, 5 - 10 subdivided to 0.02; lower scale 1 - 2 subdivided to 0.0005, 2 - 5 subdivided to 0.01, 5 - 10 subdivided to 0.05.
Reverse: six identical scales on upper stock, middle stock and two slides; marked ‘A’ on stock and ‘B’ and ‘C’ on slides. Divided 1 - 10[0], numbered by 1 to 30 and thereafter by 5; 1 - 2 subdivided to 0.02, 2 - 5 subdivided to 0.05, 5 - 10 subdivided to 0.1, 10 - 20 subdivided to 0.2, 20 - 50 subdivided to 0.5, 50 - 100 subdivided to 1. An inverted version of the scale also appears on the middle stock, marked ‘INVERTED’. Lower stock has scale marked ‘D’ and ‘GIRT LINE’, divided 4 - 40, numbered by 1; 4 - 10 subdivided to 0.05, 10 - 40 subdivided to 1/8.

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:42153