Accession No

3309

Brief Description

slide rule, by A. W. Faber, German, 20th Century

Origin

Germany; Bavaria

Maker

A. W. Faber

Class

calculating

Earliest Date

1900

Latest Date

1950

Inscription Date

Material

wood (boxwood); metal (brass); glass

Dimensions

length 260mm; breadth 32mm; thickness 12mm

Special Collection

Provenance

Donated, 1985.

Inscription

‘A.W. FABER MADE IN BAVARIA’ (obverse)

Description Notes

Boxwood slide rule with one bevelled edge. Glass cursor bound in brass.
Obverse: double radius log scale on upper part of stock and repeated on slide, divided 1 - 100, numbered 1, 1.1...2, 2.5...10, 11...20, 25...100. Single radius log scale on slide and repeated on lower part of stock, divided 1 - 10, numbered 1, 1.1...2, 2.5...10.
Reverse of slide has has scale of sines divided [30´] - [90˚], numbered 40´, 50´...2˚, [2˚]30´...10˚, 15˚...70˚, 80˚. Scale of equal parts divided [0] - 10, numbered by 0.5, subdivided to 0.02. Scale of tangents divided [5˚ 30´] - 45˚, numbered by 1˚.
Underneath slide on stock is scale of centimetres divided [26] - [52], numbered by 1, subdivided to 0.1. This is the continuation of a scale on one edge, divided [0] - [26], numbered by 1, subdivided to 0.1.
Bevelled edge carries scale of inches, divided 0 - 10, numbered by 1, subdivided to 1/64.
Reverse carries inch scale divided 0 - [10], numbered by 1, subdivided to 1/16. Also metric scale divided 0 - 25, numbered by 1, subdivided to 0.1cm.

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:42523