Slide rule (detail) (1 of 2)

This slide rule was made around 1820, and retailed by W. & S. Jones, scientific instrument makers based in London. It was designed by John Robertson (1712-76) in 1757.

It incorporates the scales of a Gunter rule for undertaking standard navigational problems. In addition, the design has a sliding brass index, or cursor, and a slow motion screw for exact adjustment for the sliding rule. This side shows the brass index or 'runner', and the wooden faces carry twelve logarithmic lines, nine fixed and three sliding. These are (from the top) sine rhumb, tangent rhumbs, versed sines below are tangents, numbers, meridial degrees to 50, meridian degrees 50 to 74 and degrees of longitude.

Robertson was master of the mathematical school at Christ's Hospital, London from 1748, and in 1755 became master of the Royal Naval Academy. Portsmouth, which he left in 1766, becoming clerk and librarian to the Royal Society in 1768. He produced a number of publications, and after his death, William Mountaine described his improved slide-rule in 1778: it was a navigator's 30-inch rule with a brass cursor which allowed the scales to be precisely matched.

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Online ID:	000-100-104-259-C
Image Rights Holder:	National Museums Scotland
Project:	0098: National Museums Scotland Project description \| View all records in project
Ref:	National Museums Scotland T.1978.94
Date:	Around 1820 c. 1820
Material:
Dimensions:	880 mm x 65 mm x 10 mm
What:	Slide-rule
Subject:
Who:	Gunter (Eponym) W. and S. Jones, London (Maker)
Where:	England, London
Event:
Description:	Slide-rule by W. and S. Jones of London, made about 1820
References:	For a biography of Robertson, see Taylor, E. G. R., The Mathematical Practioners of Hanoverian England, 1714-1840. Cambridge: 1966, p 189Cajori, Florian, A History of the Logarithmic Slide Rules and Allied instruments. Mendham, N.J. : 1994, pp 32-4 Mountaine, William, The Use of Gunter's Sector as improved by Mr John Robertson. London: 1778 Robertson, John, Treatise on Mathematical Instruments. London: 1757
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