Accession No
1084
Brief Description
astronomical quadrant, 18-inch radius, by John Bird, English, c. 1765
Origin
England; London
Maker
Bird, John
Class
astronomy
Earliest Date
1765
Latest Date
1765
Inscription Date
Material
metal (brass); glass
Dimensions
radius 460mm; overall height (max) 1120mm
Special Collection
Provenance
On loan from St. John’s College, University of Cambridge from 08/1951.
Inscription
Description Notes
Brass astronomical quadrant by John Bird, c. 1765
Plate brass lattice framework. One telescope with pivoted object glass cover fixed to reverse of one straight edge, a second pivoted at apex, with pivoted object glass cover, diagonal eyepiece attachment (eyepiece missing), clamp and micrometer tangent screws (micrometer drumhead divided 0 - 60 four times), two Verniers - one for each scale. 2 motions by racked semicircles, both handles missing, clamping and releasing knurled screws.
Limb divided with 2 scales: one -19- by 1˚ subdivided 1/8˚; the other -15- by 1˚, subdivided to 10´. This division is on an additional limb riveted onto and partly obscuring original transversal scale. The whole mounted on horizontal circle divided 0 - 180 - 0 by 1˚, with clamp and tangent screws.
Conical stand with 4 flat radial feet and 4 levelling screws.
Good condition
References
Joshua Nall; ‘The Stolen Quadrant’; Explore Whipple Collections online article; Whipple Museum of the History of Science; University of Cambridge; 2020: https://www.whipplemuseum.cam.ac.uk/explore-whipple-collections/astronomy-and-empire/stolen-quadrant
Events
Description
This quadrant was part of the equipment supplied to the new observatory at St. John’s College by Richard Dunthorne, butler and astronomical observer at Pembroke Hall. It was made by John Bird, one of the best astronomical instrument makers of the day, who had also supplied the Royal Observatory at Greenwich with observational instruments.
The quadrant has been altered by the addition of a second scale to the limb and by the replacement of the original telescopes, both of which were carried out by John Bird himself. While the old limb carries a standard degree scale, the additional scale was divided into 96 parts along the same distance as 90˚. This form of scale was introduced by Bird because it was easier to divide accurately, and so allowed the astronomer to check the accuracy of the degree scale and to ensure the best results from his observations.
12/05/2014
Created by: [From ‘Main Gallery Large Objects in the Whipple collection’ booklet] on 12/05/2014
FM:39922
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