Accession No

3014

Brief Description

Davis-Stokes slide rule, by Sivad, 1/2 20th C

Origin

Maker

Sivad

Class

calculating

Earliest Date

1900

Latest Date

1950

Inscription Date

Material

wood (boxwood); metal (white metal); plastic (ivorine); paper (card)

Dimensions

length 220mm; breadth 51mm; thickness 7mm box length 213mm; breadth 56mm; thickness 13mm

Special Collection

Steward collection

Provenance

Collection purchased from member of the Steward family, 1974.

Inscription

‘DAVIS-STOKES RULE
18 PR. Q.F. GUN’ (under one slide)
‘SIVAD’ (written under same slide)

Description Notes

Boxwood slide rule with one bevelled edge and ivorine lining to slide holders, bound with white metal rivets.
Obverse: upper part of stock has map scale for 1:20000, divided [0] - [4500], numbered by 1000, subdivided to 100. Also scale of elevation, divided [40´] - [14˚], numbered 1, 2, 3, 4, 5, 10. Also scale for range, divided 500 - [10000], numbered 500, 1000, 2000...6000. Slide has scale marked ‘base’, divided 10 - [1000], numbered 10, 20, 30, 40, 50, 100, 200...600; also scale marked ‘corrector change’ divided 2 - 20, numbered 2, 5, 10, 20, subdivided to 1; also scale marked ‘sub-base angle’, divided 3˚ - 15˚, numbered 3, 5, 10, 15, subdivided to 1˚; also scale marked ‘apex angle’, divided 10´ - [14˚], numbered 10´, 20´...1˚, 2˚...10˚. Lower part of stock has scale marked ‘height of burst’, divided 20´ - 1˚, numbered by 10´; also scale marked ‘exterior angle’, divided 20˚ - 90˚ and back to 160˚, numbered 20, 30...70, 120, 130...160.
Reverse: upper part of stock has four scales: first marked ‘air’, divided 2 - 6, numbered by 1; second marked ‘charge’, divided 2 - 6, numbered by 1; third marked ‘headwind’, divided 2 - 6, numbered by 1; fourth marked ‘barometer’ 2 - 6, numbered by 1, subdivided to 0.1; whole marked ‘setting range in 000’. Slide has four scales: first two marked ‘temp (air or charge) F’, first divided 100- - 70-, numbered by 10, second divided 20+ - 50+, numbered by 10; third scale marked ‘headwind’, divided 50+ - 10+, numbered by 10; fourth scale marked ‘barometer (inches)’, divided 27- - 29-, numbered by 1, also 31+ and 32+. Arrow near right hand end of scales. Lower part of stock has scale marked ‘correction for gunrange’, divided 10 - 100, numbered by 10. Underneath slide are two scales: first marked ‘Mk I range indicator’, divided [80] - [360], numbered by 100, subdivided to 10; second scale marked ‘100 per cent zone’, divided ±40 - ±100, numbered by 10.
Maroon card slip case (no lid).

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:42283