Accession No

0648

Brief Description

slide rule, 1st half 20th century

Origin

Maker

Class

calculating

Earliest Date

1900

Latest Date

1950

Inscription Date

Material

wood (plywood); paper; plastic (celluloid, perspex); glass; metal (white metal)

Dimensions

length 281mm; breadth 39mm

Special Collection

Cavendish collection

Provenance

Hutchinson Collection

Inscription

‘SLIDE RULE DATA SLIPS, compiled by C. N. Pickworth, Wh. Sc.’ (reverse)

Description Notes

Plywood rule faced with white celluloid. One bevelled edge carrying inch scale divided 0 - 10, numbered by 1, subdivided to 1/16. Upper part of stock carries two scales: first divided 1 - 10, numbered 1, 1[.]1, 1[.]2...2, 3...10. Second divided [0.9] - [3.3], numbered by 0.1. This scale also appears on the slide, which carries two further scales: first divided 0 - 5 and 5 - 1[0], numbered by 1, subdivided to 0.01. Second divided 3 - 1[0], numbered by 1.
Lower part of stock repeats this scale and also carries scale divided 10 - 100, numbered 10, 11, 12...20, 30...100.
Lower edge of rule carries scale divided [1.78] - [5.7], numbered by 1.
Perpsex and white metal cursor with central lens for magnifying scales.
Reverse carries various formulae and conversion factors.

Condition good (somewhat dirty); 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:42515