Accession No

2254

Brief Description

slide rule, by W. Flower, English, mid 18th Century

Origin

England

Maker

Flower, W.

Class

calculating

Earliest Date

1725

Latest Date

1775

Inscription Date

Material

wood (boxwood); metal (brass)

Dimensions

length 236mm; breadth 46mm; thickness 25mm

Special Collection

Provenance

Purchased from Turner and Devereux, London, 07/1976. Purchased with assistance a Grant-in-Aid administered through the Science Museum (PRISM).

Inscription

‘* W. FLOWER: PROJECTR. *’ (face A)

Description Notes

Boxwood slide rule with inlet brass gauging points.
Face A: upper part of stock marked with various gauging points (ends only in brass). Lower part of stock has single radius log scale marked ‘A’, divided 1 - 10, numbered by 1, with various points marked. Two slides: upper has inverted single radius log scale divided 3 - [36], numbered 3, 4...1[0], 2[0], 3[0], with gauge points marked. Lower slide has single radius log scale marked ‘C’, divided 1 - 10, numbered by 1, with various points marked. Reverse of upper slide has scale of inches divided [7.7] - 15, numbered by 1, subdivided to 0.1. Reverse of lower slide has log scale split over two edges, marked ‘E’, divided 3[0] - 4[0000], numbered 3[0], 4[0]...100, 2[00...1000, 2[000]...10000, 2[0000]...4[0000], with various other points marked along the length.
Face B: upper part of stock has single radius log scale which continues on central part of stock, marked ‘D’, divided 1 - 10, numbered 1, 2, 3, 3[.]2, 4, 5...10, with various gauging points marked. Lower part of stock has scale of inches, divided [0] - [7.5], numbered by 1, subdivided to 0.1. Upper slide has log scale split into two portions, marked ‘E’, divided 1 - 9[00], numbered 1, 2...10, 2[0]...100, 2[00]...9[00] with various gauging points marked. Lower slide (broken) has inverted single radius log scale divided 1 - 10, numbered by 1. Reverse of upper slide has single radius log scale marked ‘B’, divided 1 - [9.5], numbered by 1, various gauging points marked.
Edge A: upper part of stock has log scale of versed sines, marked ‘V. Sin’, divided [144] - [163˚ 45´], numbered by 5˚. Also a log scale of sines, marked ‘Sine’, divided 30´ - [5˚ 30´], numbered 30´, 40´, 50´, 1˚, 2˚, 3˚, 4˚, 5˚. Slide has scale marked ‘Tang Min’, divided 5´ - 30´ and back to 55´, numbered by 5´. Also a log scale of tangents, marked ‘Tang’, divided 30´ - 5˚ and 85˚ - 89˚ 30´, numbered 30´, 40´, 50´, 1˚, 2˚...5˚, 85˚, 86˚...89˚, [89˚] 10´, [89˚] 20´, [89˚] 30´. Lower part of stock has log scale of sines divided [5˚] - 90˚, numbered 6, 7...10, 20...90, with various points marked along the length. Also a scale of versed sines, marked ‘V.S’, divided 10 - [144], numbered 10, 20...140. Reverse of slide has two scales, one of ‘Sine Min’, divided [3´] - [31´], numbered 5, 10, 20, 30; the other of sines, marked ‘Sine’, divided 30´ - [5˚ 15´], numbered 30´, 40´, 50´, 1˚, 2˚...5˚.
Edge B: upper part of stock has scale of tangents, marked ‘Tang’, divided 30´ - [5˚ 30´] and also [84˚ 30´] - [89˚ 30´], numbered 30´, 40´, 50´, 1˚, 2˚...5˚ and 85˚, 86...89˚, [89˚] 10´, [89˚] 20´, [89˚] 30´. Slide has identical scale. Also scale of tangents divided [5˚] - 45˚ and back to [85˚], numbered 6, 7...10, 20, 30, 40, 45, 50, 60, 70, 80, 81, 82, 83, 84. Lower part of stock has identical scale of tangents to second scale on slide. Reverse of slide has two scales of sines: first divided [32´] - [5˚ 30´], numbered 40´, 50´, 1˚, 2˚...5˚; the second divided [5˚] - 90˚, numbered 6, 7, 8, 9, 10, 20...90˚.

Condition fair (one slide broken); 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:42487