Bronzen kwadrant, 1792
William & Samuel Jones, London,
Maker:
Collectie:
NavigArte
Bronzen demonstratie kwadrant staand en draaiend op een gegradueerde voet ( 2 x 0-180°)
The quadrant is used to take declination a Zenith distances in degrees with the aid of a quarter circle as proposed by Ptolemy. This type of quadrant is described in: The new Royal Encyclopedia, Vol. 1, Plate 5 (1788). Which is signed by G. Adams.
W&S Jones were registered on the above address between 1792-1800 (Provenance: Crijns)
The brass round baseplate has thee adjustable feet for horizontal adjustment and a 0-360 degrees scale, with 1° subdivisions for measuring the azimuth (horizontal direction) according to the magnetic north pole.
The quadrant has sighting holes at the top to adjust the angle of the rotatable quarter circle to the star or object to be measured. The obtained declination angle can then be read by a plummet line along the engraved 0-90 scale with 1° subdivisions.
The brass weight on this line is from a later date.