Accession No

5963

Brief Description

slide rule by PIC; early to mid 20th C

Origin

Maker

PIC

Class

calculating; surveying

Earliest Date

1900

Latest Date

1970

Inscription Date

Material

wood; metal (aluminium); glass; plastic (ivorine)

Dimensions

(instrument) length 581mm; width 49mm; depth 16mm (case) length 600 mm; width 59 mm; depth 24 mm

Special Collection

Brian Harland collection

Provenance

Donated on or before 22/07/2003.

Inscription

'REGD
P.IC. [logo of a pick]
'P.I.C.
No. 122' (underneath slide)
TRADE MARK' (on sliding arm)

'COPYRIGHT' (on bottom right hand corner of rule)
'PAT.NO.411090' (on top left hand corner of rule)
'W.B. HARLAND' (written on underside)

'Supplied by
W. HEFFER & SONS, LTD.
19 SIDNEY STREET,
CAMBRIDGE' (label on box)

Description Notes

Wooden slide rule with ivorine coating and aluminium framed glass with hairline. Upper part of stock:
first scale divided 1.1 - 3 numbered 1.1, 1.12, 1.14, 1.16, 1.18, 1.2, 1.25, 1.3, 1.35, 1.4, 1.45, 1.5, 1.55, 1.6, 1.65, 1.7, 1.75, 1.8, 1.9, 2, 2.1, 2.2 ... 2.9, 3 subdivided to 0.002. Second scale divided 2.6 - 105 numbered 2.6, 2.7 ... 3, 3.5, 4 ... 5.5, 6, 7...10, 15, 20 ... 50, 100 , 2, 3 ... 9, 103, 2, 3 ... 9. 104, 2, 3 ... 9, 105 subdivided to 0.1.
Third scale divided 1 - 100 numbered 1, 1, 2, 3, pi, 4 ... 10, 1, 2 ... 9, 20, 30, 40 ... 100.

Lower part of stock:
First scale divided 1 - 10 numbered1, 1, C, 2, 3 ... 9, 2, 25, 3, pi, 35, C1, 4, 45, 5, 6, 7 ... 10.
Second scale divided 1 - 1 numbered 1, 1, 2, 3 ... 9, 2, 3 ... 9, 1, 1, 2, 3 ... 9, 2, 3 ...9, 1, 1, 2, 3 ... 9, 2,3 ..9, 1.

Slide has identical scales on top and bottom edges to those on upper and lower parts respectively. First red scale numbered 1, 9, 8, 7 ... 5, 45, 4, 35, 3, 25, 2, 9, 8, 7 ... 1, 1, 9. Second red scale numbered 1.0, 9, 99, [0].99, [0].95, [0].90, [0].8 ... [0].2, 0, [0].2, [0].3 ... 1.8. Black scale on same horizontal level as red scale, numbered 60°, 50°, 40° ... 10°, 0, 20°, 30° ...90°

Inch scale on top face, from 1 - 20 inches, subdivided in 1/20ths.
cm scale on bottom face, from 1 - 50 cm, subdivided in mm intervals.

Underside has conversion scale and constants table.

Black covered cardboard sliding case, in two parts, with gold label 'Supplied by, W. HEFFER & SONS, LTD.,19 SIDNEY STREET, CAMBRIDGE'

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:46426