Accession No
2396
Brief Description
combined slide rule, sector and folding rule, by George Cox, English early 19th Century
Origin
England; Birmingham
Maker
Cox, George
Class
calculating; mathematics
Earliest Date
1800
Latest Date
1825
Inscription Date
Material
wood (boxwood); metal (brass)
Dimensions
length folded 321mm; breadth 39mm; thickness 6mm
Special Collection
Provenance
Purchased from Harriet Wynter, London, England, 11/1978.
Inscription
‘GEOE COX
MAKER
LATE
THOS COX & CO.’ (on slide rule side)
Description Notes
Boxwood folding rule with reinforced brass ends and hinge. One side carries sector scales for tangents, chords, polygons and two scales of numbers. Scale of tangents marked ‘Tang’ graduated [0] - 45 numbered by 10, divided to 1. Scale of chords marked ‘Chord’ graduated [0] - [166] numbered by 10 divided to 1. Scale of ‘POLYGONS’ divided 12 - 2 numered by 1. One scale of numbers graduated 0 - [30] numbered by 1. divided to 1/12; other scale of numbers graduated [0] - [40] numbered by 1 divided to 1/6. On fully opened limb 2 foot rule graduated [0] - [24] numbered by 1, divided to 1/8. On outer edge of one arm, decimal foot graduated [0] - [100] numbered by 10 divided to 1. On outer edge of other arm foot scale in inches graduated [0] - 12 numbered by 1, divided to 0.1. Also scale marked ‘SPHEROID’ graduated [0] - [7.5] numbered by 1, divided to 0.1. Other side of instrument carries slide rule on upper section and further scales on lower section. Two slided, one boxwood, one brass, each divided 1 - 10[0]. Same scale appears above the brass slide, engraved in the opposite direction. Furtehr scale beneath slide (purpose unknown). On lower arm scale of ‘HOURS’ graduated [0] - VI numbered by I divided to 5 minutes. Scale of ‘CORDS’ graduated [0] - 90 numbered by 10 divided to 1˚. Scale of ‘LATITUDES’ graduated [0] - [75] numbered by 10, 0 - 40 divided to 1; 40 - 70 divided to 2. Scale of ‘INCLI MERID’ graduted [0] - 90 numbered by 10 divided to 1. Four further scales of quarter inches, half inches, three-quarter inches and inches.
Condition good (slides jammed); complete
References
Events
Description
This 19th-century item combines three important instruments: the simple rule, still commonly used today; the sector, which was used in navigation, astronomy, and mathematics, and which was invented during the 16th Century; but most importantly, the slide rule.
Developed during the 17th 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 multiplication and division. 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:40152
Images (Click to view full size):
