Accession No
1218
Brief Description
quadrant, surveying, ‘Rathborne’s peractor’, by the workshop of Elias Allen, English, c. 1630
Origin
England
Maker
Workshop of Elias Allen
Class
surveying
Earliest Date
1620
Latest Date
1630
Inscription Date
Material
metal (brass)
Dimensions
length 251mm; breadth 226mm; height 175mm
Special Collection
Provenance
Purchased from Derek J. de Solla Price, in sale in Ireland, in 09/1953(?).
Inscription
Description Notes
Quadrant, surveying, ‘Rathborne’s peractor’, [by the workshop of Elias Allen], English, c. 1630. With mount for tripod.
Brass; limb calibrated 0-90, 90-180, 180-270 and 270-360˚ anti-clockwise to 15’ of arc. Scale along quadrant edges 0-100 extended to form rectilinear sine/cosine grid. Alidade with slit and window sight (wire missing). Second alidade missing. Index arm at right angles calibrated 0-100 to 1, on pivot at corner, with thumb turn attachment beneath.
Beneath is a fitting for staff or tripod with clamp. Plumb bob.
Incomplete (missing one alidade sight).
References
Events
Description
Quadrant
A quadrant is a quarter of a circle, and there are different types of instrument that come under that description. The size of quadrants varied hugely from Tycho Brahe’s highly successful huge 2m radius one, to the more portable versions of the 18th century. In all examples it was important to keep movement, wear and flexure to a minimum, especially if results were to form part of an extended research program and to be compared with one another.
The quadrant was the principle measuring instrument of astronomy in the 17th and 18th centuries, being used in all major observatories. Plain sights (where the angle was simply read off by eye) were replaced by telescopic sights in more sophisticated examples.
18/10/2002
Created by: Saffron Clackson on 18/10/2002
FM:43369
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