Brass quadrant of 23-inch radius with diagonal scales on a wrought iron stand by Butterfield of Paris. The quadrant is fitted with a telescopic sight and an enclosed plumb bob.
This fine brass and iron quadrant was displayed at the Special Loan Collection of Scientific Apparatus exhibition held at the South Kensington Museum in 1876.
Dated to the early eighteenth century, this astronomical quadrant was made by the French instrument maker Michael Butterfield in Paris. Unlike later instruments the sighting telescope is fixed to the quadrant that pivots at the centre of its graduated radial scale that is marked in degrees. The astronomical quadrant was employed to measure the angle of a celestial object from the zenith. Operated in conjunction with a transit instrument it could be used to check the running rate of astronomical clocks known as regulators. The instrument's orientation in both the horizontal and vertical could finely adjusted using both the plumb bob and spirit level.