Accession No

1084


Brief Description

brass astronomical quadrant, 18-inch radius, by John Bird, England, c. 1765


Origin

England; London


Maker

Bird, John


Class

astronomy


Earliest Date

Jan. 1, 1765


Latest Date

Dec. 31, 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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