Accession No

3399

Brief Description

slide rule, 4/4 19th Century

Origin

Maker

Class

calculating

Earliest Date

1875

Latest Date

1900

Inscription Date

Material

wood; plastic (ivorine, perspex); metal (white metal, brass); hide (leather); cloth (velvet); paper

Dimensions

length 513mm; breadth 37mm; thickness 14mm; case length 523mm; breadth 51mm; thickness 24mm

Special Collection

Provenance

Donated, 1983. Owned by A.P. Trotter and passed on to his daughter after his death who gave it to donor.

Inscription

‘APT A.P. TROTTER’ (on one edge)
‘A.P. Trotter. 121 Ashley [?] G....e’ (on stock under slide)

Description Notes

Boxwood slide rule coated in ivorine with one bevelled edge. This edge has a centimetre scale divided 0 - 5[0] numbered by 1 subdivided to 0.1. Upper part of stock has log scale divided [1] - 10[0] numbered [1.]1, [1.]2 ... 2, 3 ... 10, [1]1, [1]2 ... 2[0], 3[0] ... 10[0]. Slide has identical scale. Also second log scale divided 1 - 10 numbered 1, [1.]1, [1.]2 ... 2, 3 ... 10. Identical scale on lower part of stock.
Reverse of slide has log scale of sines marked ‘S’ divided [35’] - [90] numbered 1, 2 ... 10, 12, 14 ... 20, 25, 30, 40 ... 80. Log scale of Tangents marked ‘T’ divided [35’] - [45] numbered 1, 2, 3 .. 10, 20, 25, 30, 35, 40. Also equal scale divided [0] - 1000 numbered by 20 subdivided to 0.4. On stock underneath slide, centimetre scale divided [51] - 101 numbered by 1 subdivided to 0.1. Perspex cursor (later addition). Wooden case covered in leather and lined with purple velvet with brass hinges and hook fasteners contains business card for ‘Alex P. Trotter’ when Editor of the electrician. Various addresses appended in ink.

Condition: fair (a bit chipped); 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:42274