Accession No

1848

Brief Description

eyepiece micrometer, by John Cuff, English, 1750 (c)

Origin

England; London

Maker

Cuff, John

Class

microscopes

Earliest Date

1747

Latest Date

1772

Inscription Date

Material

metal (brass, silver); glass

Dimensions

max diameter 43mm; height 20mm; micrometer bag length 128 mm; breadth 47 mm

Special Collection

Heywood collection

Provenance

Purchased from the Professor Harold Heywood collection under estate duty exemption benefit with the assistance of a Science Museum grant-in-aid. Presumed acquired by H. Heywood from T.H. Court. Presumed purchased by T.H. Court from a Cuff instrument in the Crisp sale of 1925.

Inscription

‘I CUFF Londini Inv & Fec’
‘Silver wire micrometer from George III collection No’ (on base of case)

Description Notes

Eyepiece micrometer; made by John Cuff; English; circa 1750.

Brass; (for use in the focus of the eye-piece of a Cuff ‘Double Microscope’). Brass ring crossed with a rectilinear net of silver wire 38 x 38 strands over 72/100” forming a lattice of 0.01945” or slightly less than 1/50” sided squares.
Contained in a nineteenth century brass case with glazed lid.

Inside is some soft protective material, presumably original. Case is in 3 parts (17/03/2021)

References

Boris Jardine; 'The earliest measurements of microscopic objects'; Explore Whipple Collections online article; Whipple Museum of the History of Science; University of Cambridge; 2006: https://www.whipplemuseum.cam.ac.uk/explore-whipple-collections/microscopes/earliest-measurements-microscopic-objects

Events

Description
Micrometer
Micrometers were used mainly by astronomers and microscopists to measure objects. They were first devised in about 1609 and used the exact number of turns of a screw to measure small distances. Micrometers were inserted into the path of a telescopes and microscopes, and were also used to accurately measure quadrant scales.

Early examples of the micrometers used in telescopes were calibrated geometrically using a piece of card at a distance of about 200m with lines of known separation on it. However, this introduced inaccuracies of a few seconds of arc due to the closeness of the card compared with the distance of real observations. It was not until 1672 that this problem was overcome and accurate calibration was possible.

18/10/2002
Created by: Saffron Clackson on 18/10/2002

FM:42699