Accession No
0979
Brief Description
glass ruled micrometer slide and micrometers; English; circa 1800
Origin
England
Maker
Class
microscopes
Earliest Date
1800
Latest Date
1800
Inscription Date
Material
fishskin (shagreen); glass; ivory; metal (brass); wood
Dimensions
length of case 97mm; breadth 24mm; thickness 19mm
Special Collection
Robert Whipple collection
Provenance
Inscription
Description Notes
Glass ruled micrometer slide in brass mount, marked ‘50’. Two ruled ivory micrometers, one a grid, the other a scale.
Wooden slip case covered in black shagreen.
Condition fair (some corrosion to micrometer slide); complete
References
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:40069
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