Accession No

2300

Brief Description

gauging and proof slide rule, by J. Long, English, mid-19th Century

Origin

England; London; 20 Little Tower Street

Maker

Long, J.

Class

calculating

Earliest Date

1825

Latest Date

1875

Inscription Date

Material

ivory; metal (white metal)

Dimensions

length 170mm; breadth 42mm; thickness 6.5mm

Special Collection

Provenance

Purchased from D.H. & R.A. Morgan, Norfolk, England, 18/4/1977.

Inscription

‘J. LONG 20 LITTLE TOWER STREET LONDON’ (edge)

Description Notes

Ivory slide rule bound with metal ends and with two ivory slides.
Obverse carries scales for gauging. Double log scale repeated on stock (marked ‘A’), twice on one slide (marked ‘B’ and ‘C’) and once on the second slide (marked ‘N’); divided 1 - 10[0], numbered 1, 2...1[0], 12, 2[0], 3[0]...10[0], 1 - 3 subdivided to 0.05, 3 - 7 subdivided to 0.1, 7 - 10 subdivided to 0.2, 10 - 30 subdivided to 0.5, 30 - 70 subdivided to 1, 70 - 100 subdivided to 2. Inlet gauge points on scale A at ‘IMB’ and ‘IMG’. Central part of stock carries scale marked ‘D’, divided 1 - 10, numbered by 1, 1 - 2 subdivided to 0.02, 2 - 5 subdivided to 0.05, 5 - 10 subdivided to 0.1; inlet gauging points at ‘IG’, ‘MS’ and ‘MR’. Also ullaging scale of segments standing, marked ‘SEG. ST’ and ‘S.ST’, divided [0.8] - 100, numbered 1, 2, 3...10, 20...100; 0.8 - 5 subdivided to 0.1, 5 - 10 subdivided to 0.2, 10 - 50 subdivided to 1, 50 - 100 subdivided to 2. Lower part of stock carries ullaging scale of segments lying, marked ‘SEG.LY’ and ‘S.LY’, divided [0.5] - 100, numbered 1, 2, 3...10, 20...100; 0.5 - 4 subdivided to 0.1, 4 - 7 subdivided to 0.2, 7 - 10 subdivided to 0.5, 10 - 50 subdivided to 1, 50 - 100 subdivided to 2.
Reverse carries scales for proof calculations. Upper part of stock has scale marked ‘A, divided [1.5] - 8, numbered by 1, subdivided to 1/12. Central part of stock carries two scales: one marked ‘A’, divided [6.25] - 30, numbered by 1, 6.25 - 12 subdivided to 1/12, remainder subdivided to 1/6; inverted scale marked ‘C’, divided 50 - [2]40, numbered by 10, 50 - 150 subdivided to 1, remainder subdivided to 2. Lower part of stock has inverted scale marked ‘C’, divided 17 - 80, numbered by 10, subdivided to 1. Both slides carry scale marked ‘PROOF’, divided [65] - [0] - 60, numbered by 10, subdivided to 1.
Edge has scale of inches divided [0] - [6.5], numbered by 1, subdivided to 0.1. Also two scales for varieties of casks: one marked ‘SPHD’ (spheroid), divided [0] - [4.5], numbered by 1, subdivided to 0.1; one marked ‘2ND VAR’, divided [0] - 4, numbered by 1, subdivided to 0.1.

Condition good (some markings rather faded); 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:39558