Accession No

2297

Brief Description

Pilot balloon slide rule by Stanley, 1/2 20th C.

Origin

London; England

Maker

Stanley

Class

calculating

Earliest Date

1900

Latest Date

1950

Inscription Date

Material

wood; metal (brass); plastic (perspex, ivorine)

Dimensions

length 630mm; breadth 61mm; thickness 20mm; box length 652mm; breadth 79mm; height 34mm

Special Collection

Provenance

Purchased from Peter Delehar, 02/1975.

Inscription

‘Pilot Balloon Slide Rule [monogrammed MO] 1897/43 Mark II stanley london’ (front)
‘IMPORTANT Normally, number of graticule scale divisions per radian (K) x length of tail in feet (I) = 1.2 x 105.
I in other cases multiply graticule readings by 1.2/K before calculation on rule.’ (back)

Description Notes

Wooden slide rule with ivorine coating and 4 brass bound perspex indices. Upper part of stock:
cosine scale divided 89 - [0] numbered 89, 88 ... 80, 75, 70, 65 60, 50, 40, 30, 20, 15, 10, 5; 20 - 0 subdivided to 1˚. Second scale divided 80 - [0] numbered 80, 75, 70, 65, 60, 50, 40, 30, 20, 15, 10, 5; 20 - 0 subdivided to 1˚. (These scales use subdivisions on sine scale for the remainder of their length).
Sine scale divided 0.5 - 90 numbered .5, .6, .7, .8, .9, 1, 2, 3 ... 10, 15, 20, 25, 30, 40, 50, 60, 70, 90; 0.5 - 1 subdivided to 0.01, 1 - 10 subdivided to 0.1, 10 - 30 subdivided to 30’, 30 - 70 subdivided to 1˚. Second scale divided 10 - 90 numbered 10, 15, 20, 25, 30, 40, 50, 60, 70, 90; 10 - 30 subdivided t 30’, 30 -70 subdivided to 1˚.

Lower part of stock:
Secant2 Scale divided [0] - [63] numbered by 10 subdivided to 1
Tangent scale divided 3˚ - [84.3˚] numbered 3, 4, 5 ... 10, 15, 20, ... 80; 3 - 10 subdivided to 0.1, 10 - 80 subdivided to 30’, 80 - 84.3 subdivided to 0.1

Slide has log scale on upper edge divided 1 - 10[00] numbered 1, 11, 12, 13 .. 19, 2, 25, 3, 35, 4, 45, 5, 6 ... 19, 2, 25, 3, 35, 4, 45, 5, 6 ... 19, 2, 25, 3, 35, 4, 45, 5, 6 ... 10; 1 - 2 subdivided to 0.01, 2 - 5 subdivided to 0.05, 5 - 20 subdivided to 0.1, 20 - 50 subdivided to 0.5, 50 - 200 subdivided to 1, 200- 500 subdivided to 5, 500 - 1000 subdivided to 10.
Inverted log scale on left hand part of bottom edge divided 0.16 - 16 numbered 16, 17, 18, 19, 2, 25, 3, 35, 4, 45, 5, 6 ... 16; .16 - 2 subdivided to 0.01, 2 - 5 subdivided to 0.05, 5 - 16 subdivided to 0.1.
On right hand part of bottom edge, identical log scale to that on upper part but starting from 8.

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:39568