Accession No

3183

Brief Description

mathematical model illustrating the ratio of the circle, by John Harris, English, late 18th Century

Origin

England

Maker

Harris, John

Class

mathematics; demonstration

Earliest Date

1780

Latest Date

1800

Inscription Date

Material

wood; metal (brass, other)

Dimensions

length 278mm; breadth 149mm; height 300mm

Special Collection

Provenance

Purchased from Historical Technology Inc., Masssachustts, USA, 1984.

Inscription

‘MECHANICO-MATHEMATICAL INSTRUMENT
ILLUSTRATING THE RATIO OF THE CIRCLE
BY JOHN HARRIS ‘

Description Notes

Wooden base with 4 turned legs carries flat brass plate held by 4 screws. On this is mounted a vertical brass plate (held by 2 screw-fitted brass brackets, and a racked bat, held by 2 screws, with a silvered scale divided 1 - 10. Vertical plate carries a racked horizontal rod movd by pinion with knurled knob. Rod moves silvered brass sector engraved with radiating lines from centre, marked 1 - 10 which intersect 2 scales divided 1 - 10 on a horizontal bar. A silvered circle with 8 apertures turns to indicate each of the line numbers in turn; a pointer at the centre or apex of the sector moves across a scale divided 1 - 10 on the brass plate.

References

Events