Accession No
1137
Brief Description
Douglas reflecting protractor, by Cary, English, 1870 (c)
Origin
England; London
Maker
Cary
Class
surveying
Earliest Date
1870
Latest Date
1870
Inscription Date
8-10-1890
Material
metal (brass); glass; wood
Dimensions
length 150mm; breadth 85mm; height 25mm box length 163mm; breadth 109mm; height 40mm
Special Collection
Provenance
Donated by Pollen Esq.
Inscription
‘Patent 286’ (on radius arm)
‘Cary, London.’ (on Arc)
Description Notes
Douglas reflecting protractor, by Cary, c.1870.
Brass. Bevelled straight edge graduated 0-1760 (yards), numbered by 100, divided to 10. Divided on upper edge by diagonals to 1 (yard). Protractor arc divided 0-130˚, numbered by 10˚, divided to 30´. Pinhole sight on bar with half silvered horizon glass. Index glass fixed over radius. Vernier on radius arm. Reads scale to 2´ of arc.
Fitted wooden box with hand written label. Dated 8-10-1890.
Condition good; complete.
References
Events
Description
This is a drawing instrument, used to measure or plot angles on a paper chart. The protractor measures the angle between two points, using a half-silvered horizon glass, on the same principle as a sextant. With the radius arm then fixed, the protractor can be laid on the chart and a line drawn from the radius extension directly onto the paper.
Sir Howard Douglas, Royal Artillery, patented the protractor in 1811; it was made in London by the firm of Cary.
10/03/2009
Created by: Dr. Anita McConnell on 10/03/2009
FM:39606
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